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{{DISPLAYTITLE:Rolex 3131 Bubbleback}}
{{#seo:
{{#seo:
|title=Rolex Oyster Perpetual "Bubbleback" 3131 — BezelBase
|title=Rolex Bubbleback 3131 (1936–1948) — Production and dial guide | Rolexopedia
|description=The 3131 is the reference where the Bubbleback grows up. Three years after ref 1858 introduced the Perpetual rotor in an Oyster case, Rolex simplified the…
|description=Reference guide to the Rolex Oyster Perpetual 3131, introduced around 1936 with a two-piece Oyster case, caliber 620, subsidiary seconds and documented 9K, 14K and 18K gold examples.
|keywords=Rolex, 3131, Bubbleback, specifications, reference guide
|keywords=Rolex, 3131, Bubbleback, specifications, reference guide
|type=article
|image=Ref_3131_hero.webp
|image_alt=Rolex Bubbleback 3131 hero
|type=Article
|og_type=article
|published_time=2026-04-17T21:04:13Z
|modified_time=2026-08-04T00:11:47Z
|robots=index,follow,max-image-preview:large
}}
}}


[[File:Ref3131_phillips_14k_yg_front.jpg|thumb|right|300px|Rolex 3131 in 14K yellow gold, case 412931 (Phillips NY 2022, sold USD 18,900).]]


<small>[[Reference:bubbleback|Bubbleback]] → '''3131'''</small>
<small>[[Reference:bubbleback|Bubbleback]] › '''3131'''</small>


The 3131 is the reference where the Bubbleback grows up. Three years after ref 1858 introduced the Perpetual rotor in an Oyster case, Rolex simplified the case architecture. In 1936 the 3131 and its sweep-seconds twin 3132 arrive with a two-piece Oyster: the caseback screws directly into the case middle, and the separate bezel ring disappears. From that point forward every Rolex Oyster of consequence uses the same two-piece logic. The 3131 is the hinge on which that transition turns. It is also, deliberately and exclusively, a precious-metal watch.
<div class="rp-lead">
[[File:Ref_3131_hero.webp|thumb|center|640px|alt=Rolex Bubbleback 3131|Rolex Bubbleback 3131]]
</div>
 
The 3131 is an early Rolex Bubbleback with the two-piece Oyster case. Around 1936, the 3131 and its sweep-seconds companion 3132 used a caseback that screws into the case middle, with the bezel formed as part of that middle rather than as a separate ring. Published auction and specialist records show 9K, 14K and 18K yellow- and pink-gold examples. The indexed record contains no confirmed steel 3131.


<span id="core-facts"></span>
<span id="core-facts"></span>
== Core facts ==
==Core facts==


{| class="wikitable"
{| class="wikitable rp-facts"
|-
|-
! detail
! detail
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|-
|-
| movement
| movement
| Cal. 620 (9¾’’’ NA, sub-seconds at 6)
| Cal. 620 (9¾′′′ NA, sub-seconds at 6)
|-
|-
| companion reference
| companion reference
Line 54: Line 64:
|-
|-
| italian nickname
| italian nickname
| ''ovetto'' (“little egg”), per Italian auction usage
| ''ovetto'' ("little egg"), per Italian auction usage
|}
|}


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== Where it sits in the line ==
== Where it sits in the line ==


The 3131 is the first two-piece Oyster case Bubbleback. That single sentence carries most of the reference’s significance.
The 3131 is an early two-piece Oyster-case Bubbleback.


Earlier first-generation Bubblebacks (1858, 3458) used a more complex case construction with a separate movement-holder ring; the 3131 simplified this to a two-piece case with the bezel fixed and only the caseback removable. In 1936 Rolex paired two new references on the same case platform. The 3131 carried Cal. 620 with subsidiary seconds at 6 o’clock. The 3132 carried Cal. 630 with a centre sweep seconds hand. Both used an identical two-piece case: a tonneau mid-case with integrated lugs, closed at the back by a screw-down caseback that threaded directly into the case middle. No separate bezel ring. No discrete movement holder. This is the construction standard that the Submariner, GMT-Master, Datejust, and Daytona inherit.
Earlier Bubblebacks used other case constructions. The 3131 uses a two-piece form that appears across later Bubbleback references, although details still vary by reference and period.


Within its own production run, the 3131 does not evolve in the way the 1016 Explorer or the 5513 Submariner do. It is a shorter-lived reference. Surviving examples span roughly 1936 through the late 1940s, and the variation happens in dials, hands, and case materials rather than in generations of movements or case revisions. The 3131 and 3132 were sold side by side. A buyer in 1938 could choose subsidiary seconds or sweep seconds in the same case, at roughly the same price, in the same metals. Most surviving examples across both references are in comparable states of scarcity, with the sub-seconds 3131 slightly more commonly encountered at auction.
Within its run, surviving 3131 examples show variation in dials, hands, case metals and retailer signatures. The 3131 and 3132 were companion references: the 3131 has subsidiary seconds, while the 3132 uses an indirect centre-seconds drive. Auction frequency is not a reliable measure of original production or survival, so the page does not infer a ratio.


<span id="the-transition-it-completes"></span>
<span id="the-transition-it-completes"></span>
=== The transition it completes ===
=== The transition it completes ===


The arc from 1858 to 3131 runs three years and covers the entire experimental phase of the Oyster Perpetual. The 1858 proves that a 360-degree rotor can be built into a waterproof case. The 3458 proves it can be scaled to production. The 3131 proves the case itself can be simplified without losing waterproofness. Every Bubbleback after 1936 (through ref 8050 in the mid-1950s, and every Oyster descended from that lineage) is built on the two-piece logic the 3131 introduces.
The references before 3131 establish the early Oyster Perpetual and its automatic rotor. The 3131 and 3132 then document the two-piece case form that becomes common among later Bubblebacks. That is a useful case-history marker, but surviving examples do not prove that later Oysters used identical construction.


The 3131 is where the Bubbleback stops being an experimental platform and becomes a mature production design. The rotor works. The case works. The movement is reliable enough that Rolex can offer it in solid gold at premium retail prices without hedging. From here, the story becomes about variants and refinement rather than architecture.
The 3131 falls in the pre-war and wartime Bubbleback period. Its surviving variants are best described through case, movement, dial and hallmark evidence rather than through an assumed production strategy.


<span id="the-two-piece-case"></span>
<span id="the-two-piece-case"></span>
== The two-piece case ==
== The two-piece case ==
The defining technical feature of the 3131 is its case construction. On the earlier first-generation Bubbleback architecture, the bezel, mid-case, movement-holder ring and caseback combined as distinct parts to make the sealed Oyster unit. The two-piece case eliminates the internal ring. The bezel is integral to the mid-case, with the lugs, crystal seat and outer profile formed as one component. The caseback screws directly into threads cut into the mid-case.


[[File:Ref3131_phillips_14k_yg_front.jpg|thumb|right|300px|Rolex 3131 in 14K yellow gold, case 412931 (Phillips NY 2022, sold USD 18,900).]]
The two-piece form reduces the number of sealing surfaces and makes the case thinner. Because the bezel is part of the mid-case, damage to one component affects the other.
 
[[File:Ref3131_phillips_14k_yg_caseback.jpg|thumb|right|300px|The 3131's bubble caseback — screwing directly into the case middle.]]


The defining technical feature of the 3131 is its case construction. On the earlier first-generation Bubbleback architecture, the bezel, mid-case, movement-holder ring, and caseback combined as distinct parts to make the sealed Oyster unit. The two-piece case eliminates the internal ring entirely. The bezel is integral to the mid-case, turned from the same block of metal, with the lugs, the crystal seat, and the outer profile all part of a single component. The caseback screws directly into threads cut into the mid-case itself. Two pieces. That is the whole shell.
The 3131 case carries the Oyster Watch Co. signature on the caseback interior along with period-correct patent markings and hallmarks. Reference numbers between the lugs are not standard on the published 3131 examples; the reference is often engraved on the caseback interior, consistent with pre-1948 practice. Serials appear between the lugs at 6 o'clock on documented examples.


Several consequences follow. The case is thinner than it could have been with the earlier construction, with fewer interfaces between parts and fewer tolerances to stack up. Waterproofness becomes more reliable in manufacturing because there is one fewer sealing surface to get right. Service becomes simpler: a watchmaker removes the caseback and the movement lifts out directly. Production cost drops, with fewer parts, fewer machining operations, and fewer assembly steps. Against those gains, Rolex accepts one trade-off: the bezel is the mid-case, so damage to one damages the other. For a waterproof watch destined for decades of service, Rolex evidently judged the trade-off acceptable. It never reverted.
<gallery mode="packed" heights="180">
 
File:Ref_3131_caseback.webp|alt=Rolex 3131 caseback|Rolex 3131 screw-down caseback
The 3131 case carries the Oyster Watch Co. signature on the caseback interior along with period-correct patent markings and hallmarks. Reference numbers between the lugs are not standard on 3131s; most surviving examples have the reference engraved only on the caseback interior, consistent with the pre-1948 Rolex convention. Serials appear between the lugs at 6 o’clock, following the 1926-onward Oyster standard.
File:Ref3131_phillips_14k_yg_front.webp|alt=Rolex 3131 in 14K yellow gold, case 412931 (Phillips NY 2022, sold USD 18,900).|Rolex 3131 in 14K yellow gold, case 412931 (Phillips NY 2022, sold USD 18,900).
File:Ref3131_phillips_14k_yg_caseback.webp|alt=The 3131's bubble caseback, screwing directly into the case middle.|The 3131's bubble caseback, screwing directly into the case middle.
</gallery>


<span id="dimensions"></span>
<span id="dimensions"></span>
=== Dimensions ===
=== Dimensions ===


Case diameter is reported variously as 32mm, 32.5mm, and 33mm. The variance reflects different measurement points on a tonneau case. On the wrist the 3131 reads as a small-to-medium dress watch, comparable in presence to a 32mm round case. Thickness is a more meaningful figure than diameter on any Bubbleback, because the dome is the point. On the 3131 the dome is more pronounced than on the earlier 1858: the Cal. 620 rotor is physically larger and heavier than the Cal. 520 it descends from, and the caseback rises higher to clear it.
Case diameter is reported variously as 32mm, 32.5mm and 33mm. The measurement point matters on a tonneau case; Phillips records 32mm for its 1946 example. The domed caseback contributes more to the watch’s profile than the small differences in diameter. Caliber 620 and its rotor require that clearance, but surviving cases should be measured individually.


<span id="the-cal.-620"></span>
<span id="the-cal.-620"></span>
== The Cal. 620 ==
== The Cal. 620 ==


Cal. 620 is a 9¾’’’ automatic movement with 17 jewels, 18,000 bph, and a 35–41 hour power reserve depending on rotor winding state. The movement blank measures 26.4mm in diameter by 7.5mm in height, wider and flatter than it looks given how much of the 3131’s perceived thickness comes from the caseback dome rather than the movement itself.
Cal. 620 is a 9¾′′′ automatic movement commonly listed with 17 jewels and an 18,000 bph frequency. Published sources give different reserve figures, so the running time belongs to the serviced movement rather than to a fixed reference specification. The caseback dome contributes substantially to the profile.


Architecturally, Cal. 620 is an evolution of the Cal. 520 that powered the first Bubblebacks. Both share the same 360-degree unidirectional rotor, both use a Swiss lever escapement, both carry a Breguet overcoil hairspring, and both descend from the manual-wind Cal. 600 base. Cal. 620 upgrades Cal. 520 in two ways that matter. The first is the Super Balance, Rolex’s simplified monometallic balance introduced in 1935 that replaced the cut bimetallic balance used on earlier movements; less finicky to regulate and more stable across temperature ranges. The second is the rotor mass. The Cal. 620 rotor is physically larger, which improves winding efficiency at the cost of case thickness. This is the direct reason the 3131’s dome is more pronounced than the 1858’s.
Cal. 620 follows the earlier 520 family. Its rotor and winding layout are part of the reason the Bubbleback case needs additional clearance, but a case profile alone does not establish a particular movement revision.


Cal. 620 is unidirectional: the rotor spins freely in one direction and winds in the other. True bidirectional winding in a Rolex movement arrives only with Cal. 1030 in 1950, which is also the movement that ends the Bubbleback era by enabling a thin flat caseback.
Cal. 620 is unidirectional: the rotor spins freely in one direction and winds in the other. True bidirectional winding in a Rolex movement arrives only with Cal. 1030 in 1950, which is also the movement that ends the Bubbleback era by enabling a thin flat caseback.


Cal. 620 was developed under Emile Borer at Aegler, who had led the 1931–1933 Perpetual patent work that produced Cal. 520. Rolex paid royalties to Aegler on every unit produced. The “in-house” framing often applied to Rolex movements of this era is a design-authorship claim, not a manufacturing-ownership one: Rolex owned the designs progressively from 1913 onward, Aegler built them exclusively for Rolex, and the Bienne manufacturing plant did not come fully under Rolex ownership until decades later.
Caliber 620 belongs to the Aegler-built Rolex movement lineage. Corporate ownership, design authorship and manufacturing responsibility changed over time; the article does not use “in-house” as a shorthand for all three.


On the 3131, Cal. 620 runs with sub-seconds at 6 o’clock. The companion 3132 used Cal. 630, the same base movement modified to drive a centre sweep seconds hand through an indirect drive arrangement. Sweep seconds cost marginally more to build and were marketed as the modern option; sub-seconds in 1936 was the conservative register choice, readable, traditional, and the convention for most dress watches of the era.
On the 3131, Cal. 620 drives subsidiary seconds at 6 o'clock. The companion 3132 used Cal. 630, a related movement with an indirect drive for centre sweep seconds. The two references should be distinguished by the movement and dial layout, not by an assumed price or buyer preference.


<span id="precious-metals-only"></span>
<span id="precious-metals-only"></span>
== Precious metals only ==
== Precious metals only ==


[[File:Ref3131_pink_gold.jpg|thumb|right|300px|Rolex 3131 in pink gold — one of several precious-metal variants.]]
The documented 3131 record is concentrated in precious metals. Auction and specialist examples include 9K, 14K and 18K yellow- and pink-gold cases. The indexed examples are precious metal; that surviving record is not a production census.


Unlike the 1858 and 3458, which exist in steel, gold, Rolesor two-tone, and gold-filled variants, the 3131 is, as far as the documented auction and dealer record runs, a precious-metal-only reference. Five case materials appear in the surfaced corpus.
The best-documented 14K yellow gold example is the Phillips NY Watch Auction SEVEN 2022 lot (case 412931, c.1946), sold with its original Rolex hangtag, an unusual survival on a watch approaching 80 years old.


The best-documented 14K yellow gold example is the Phillips NY Watch Auction SEVEN 2022 lot (case 412931, c.1946), sold with its original Rolex hangtag, an unusual survival on a watch approaching 80 years old.
14K pink gold is the Sotheby's Watches Online 2020 configuration (case 473634, c.1946, silvered dial). The alloy differs from 18K pink gold, and the cited examples include North American-market watches.


14K pink gold is the Sotheby’s Watches Online 2020 configuration (case 473634, c.1946, silvered dial). The alloy reads warmer and softer than 18K PG and is more commonly encountered in the North American market.
18K yellow-gold examples appear in auction and dealer listings. Assay marks vary with the market of sale, so the caseback and lugs need to be read on each watch.


18K yellow gold is the most commonly surfacing 3131 material across general auction and dealer listings. 18K YG examples carry Swiss or French assay marks on the caseback and lugs, depending on the market the watch was originally sold into.
An 18K pink-gold example appears in the Sotheby's Watches Weekly Geneva 2020 record (case 51699, c.1938, pink dial). The catalogue describes its bracelet; original delivery still needs watch-specific proof.


18K pink gold shows up in the Sotheby’s Watches Weekly Geneva 2020 example (case 51699, c.1938, pink dial), early-production and a watch that ran on its original Rolex bracelet from delivery through its 2020 consignment.
9K gold examples are associated with British-market watches in the specialist record. The alloy and hallmark should be verified from the case; a dealer listing alone does not establish the intended sales market or an original price position.


9K gold was a UK-market metal standard (37.5% pure gold, compared to 58.3% for 14K and 75% for 18K), permitted for hallmarking in Britain but not in most continental European markets. 9K 3131 examples exist in dealer records and represent the lower-priced end of the precious-metal range, targeted at the British Commonwealth market.
The indexed sources contain no confirmed stainless-steel 3131. That absence does not prove that no other material variant was made.


The absence of confirmed stainless steel 3131 examples is worth stating directly. Broader Bubbleback production includes steel and Rolesor extensively (1858, 3458, 2940, 2764, and 3065 all carry documented steel variants), but the 3131 as a reference appears not to have been offered in non-precious materials. The precise reason is not documented in Rolex paperwork. A reasonable inference from the pattern of surviving examples is that the 3131/3132 pairing was positioned as the premium two-piece Bubbleback at introduction, with steel and Rolesor production routed to other references in the same family that shared the two-piece case architecture once it became the Oyster standard.
[[File:Ref3131_pink_gold.webp|thumb|right|300px|alt=Rolex 3131 in pink gold, one of several documented precious-metal variants.|Rolex 3131 in pink gold, one of several documented precious-metal variants.]]


<span id="the-suffix-system"></span>
<span id="the-suffix-system"></span>
=== The suffix system ===
=== The suffix system ===


The Vintage Rolex Field Manual’s Bubbleback suffix system applies to the 3131. Within the precious-metal-only corpus, the relevant variants are:
The Vintage Rolex Field Manual's Bubbleback suffix system applies to the 3131. Within the precious-metal-only corpus, the relevant variants are:


* '''3131/7''' — solid gold (yellow or rose; color not encoded in the suffix)
* 3131/7 — solid gold (yellow or rose; color not encoded in the suffix)
* '''3131/8''' — alternate solid gold (typically used to distinguish karat, e.g. 14K vs 18K)
* 3131/8 — alternate solid gold (typically used to distinguish karat, e.g. 14K vs 18K)


The suffix codes were period-authentic (Rolex used them internally on parts lists and service paperwork c.1933–1953) but were rarely engraved on casebacks. Most surviving 3131 casebacks carry only the four-digit “3131” without the slash variant. The suffix must be inferred from the hallmarks and dial rather than read off the case directly. A seller claiming a specific /7 or /8 variant without hallmark documentation should be treated cautiously.
The suffix codes were period-authentic (Rolex used them internally on parts lists and service paperwork c.1933–1953) but were rarely engraved on casebacks. Most surviving 3131 casebacks carry only the four-digit "3131" without the slash variant. The suffix must be inferred from the hallmarks and dial rather than read off the case directly. A seller claiming a specific /7 or /8 variant without hallmark documentation should be treated cautiously.


<span id="dial-and-hand-variants"></span>
<span id="dial-and-hand-variants"></span>
== Dial and hand variants ==
== Dial and hand variants ==


The 3131 sits in a period when Rolex dials were still largely bespoke (retailers could specify signatures, markers, and finishing within a catalog of options), and the result is a dial variety that does not map neatly onto production generations. White and silvered dials are the most commonly encountered baseline, often with applied gold Arabic numerals and a sub-seconds register at 6. Cream and ivory dials appear on yellow gold cases with the same marker convention but a softer background. Pink and salmon dials are the signature configuration for 18K PG and 14K PG cases. The Sotheby’s Watches Weekly 2020 example (case 51699, 18K PG) carries a pink dial matched to the case.
The 3131 record shows white and silvered dials, often with applied gold Arabic numerals and subsidiary seconds at 6. Cream and ivory dials also appear. Pink and salmon dials are documented on some pink-gold cases, including the Sotheby's Watches Weekly 2020 example (case 51699). Retailer signatures and dial finishing vary by surviving watch.


The case-matched dial is the signature look. Beige dials sit between cream and pink. Black dials are very rare on the 3131 and carry a premium that reflects both their scarcity and the striking contrast of black lacquer against yellow or rose gold, a configuration that ran against the dominant design language of the era. Applied gold Arabic numerals are the most commonly documented marker convention, with batons and Arabic-plus-baton combinations also appearing. Grene textured dial surfaces (a lightly grained or “hammered” finish) appear on particularly well-preserved examples and are one of the features that separates a top-tier original 3131 dial from a refinished one; refinishers generally cannot reproduce the grene texture convincingly.
Beige and silvered dials are common in the published record. Black dials and grene-textured dials need close inspection because refinishing and later dial work are common on watches of this age; texture alone does not prove originality.


Three hand configurations appear. Luminous pencil hands are the most common, with straight pencil-style hour and minute hands and radium fill that has aged to a warm orange or brown patina. Feuille (leaf) hands appear on a smaller subset, typically paired with silvered or cream dials, and give the watch a more formal dress-watch character. Spade hands are the rarest of the three, with only a handful of documented examples, typically on early pre-1940 production.
Published examples show pencil, feuille and spade hand forms. Luminous material and patina should be assessed from the individual hands and dial; hand style alone does not establish a production date.


<span id="auction-and-market-record"></span>
<span id="auction-and-market-record"></span>
== Auction and market record ==
== Auction and market record ==


Public auction records for the 3131 are thinner than for a Submariner or a Datejust reference, but substantially richer than for the vanishingly rare 1858. Three well-documented lots across Phillips and Sotheby’s anchor the modern auction picture.
The cited auction record contains one realised Phillips result and two Sotheby's estimates. These lots show documented examples, not a complete market series.


{| class="wikitable"
{| class="wikitable"
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| '''USD 18,900''' (est USD 8k–16k)
| '''USD 18,900''' (est USD 8k–16k)
|-
|-
| Sotheby’s Watches Online
| Sotheby's Watches Online
| 2020
| 2020
| —
| —
Line 176: Line 187:
| est CHF 5,000–7,000
| est CHF 5,000–7,000
|-
|-
| Sotheby’s Watches Weekly Geneva
| Sotheby's Watches Weekly Geneva
| 2020
| 2020
| —
| —
Line 186: Line 197:
|}
|}


The Phillips NY 2022 result is the headline data point. A 14K YG 3131 sold for USD 18,900 against an estimate of USD 8,000–16,000, on a watch that retained its original Rolex hangtag (the small paper card affixed at the factory and typically removed by the first owner on receipt). Hangtag survival on a mid-1940s Rolex is extraordinary; it effectively pushes the watch into a provenance tier above its configuration peers.
The Phillips NY 2022 lot was a 14K yellow-gold 3131 that sold for USD 18,900 against an estimate of USD 8,000–16,000. The catalogue records an original Rolex hangtag with a handwritten serial number. That accessory is part of the lot’s provenance; it does not establish a general premium for every 3131.


The two Sotheby’s 2020 lots sit at more typical market levels. Both were estimated in the low-to-mid four-figure CHF range, which maps reasonably onto broader dealer pricing for the reference. Collectors Square data covering the same period shows 3131 examples trading in the EUR 2,516–5,100 range, suggesting that the reference’s baseline market for unrestored original-dial examples in good condition sits in roughly the EUR 3,000–5,000 / CHF 3,000–6,000 band. Premium-tier examples (hangtag survival, exceptional dial condition, early production 18K PG on original bracelet) can reach the USD 15,000–20,000 range observed at Phillips.
The two Sotheby's 2020 lots were estimated in the CHF 4,000–7,000 and CHF 4,000–6,000 ranges shown in the table. Those estimates should be read with the lot descriptions and condition; they are not a general valuation band.


<span id="case-number-observations"></span>
<span id="case-number-observations"></span>
=== Case number observations ===
=== Case number observations ===


The three documented cases span roughly 51,699 (c.1938) through 473,634 (c.1946), a serial range consistent with 1936–1948 production dating per the standard Dowling/Hess reconstruction. The 412,931 and 473,634 cases, both dated to roughly 1946, sit within a tight serial window and likely reflect a concentrated late-production batch. No confirmed 3131 example post-1948 has surfaced in the indexed auction record, which supports the standard end-of-production estimate in the late 1940s.
The three documented cases span roughly 51,699 (c.1938) through 473,634 (c.1946), a range consistent with the broad 1936–1948 dating used by the family guide. The sample is too small to infer production batches. The indexed auction record contains no confirmed post-1948 example; that absence does not establish an end date.


The pattern matches what would be expected for a reference that was introduced in 1936, gained traction through the late 1930s, continued through the war years (with reduced production volumes reflecting the broader Swiss watch industry contraction), and was gradually replaced by newer two-piece Bubblebacks (3065, 3372, 4220, early 4467) through the mid-to-late 1940s. Exact production totals are not documented in any public source.
The reference is generally placed in the late-1930s and 1940s Bubbleback period. Later two-piece references, including 3065, 3372, 4220 and early 4467 examples, overlap the same broad era. Exact production totals and a precise replacement date are not documented in the cited sources.


<span id="what-the-3131-established"></span>
<span id="what-the-3131-established"></span>
== What the 3131 established ==
<span id="What_the_3131_established"></span>
== Place in Bubbleback history ==


Three features of the 3131 persist across Rolex production for decades after the reference itself ends.
The 3131 records two early Rolex design developments: the two-piece Oyster case and the 620-family automatic movement.


The two-piece Oyster case becomes the platform for every sport and dress Oyster that follows. Every Bubbleback from 1936 forward (2940, 2764, 3065, 3372, 4220, and the entire 1940s Datejust lineage) uses the same two-piece logic. By the time the Submariner launches as ref 6204 in 1953, the two-piece case is so thoroughly the standard that no one talks about it as a design decision. It is simply how Rolex makes waterproof watches.
The two-piece Oyster case appears across many later Bubbleback references, including 2940, 2764 and 3065. The exact case, bezel and movement details still need to be checked by reference; this page uses the 3131 as an early dated example of the form.


Cal. 620 establishes the automatic movement architecture that serves the Bubbleback era through its transitional 630, 635, and 645 variants into the early 1950s. When Cal. 1030 arrives in 1950 and ends the Bubbleback dome by enabling a flat caseback, it inherits the same 360-degree rotor principle that Cal. 620 embodied. The bidirectional winding is new in Cal. 1030; the rotating-mass-drives-the-mainspring concept runs from 1858 through 3131 through Cal. 1030 and into every Rolex automatic that follows.
Cal. 620 sits in the 620/630/635/645 movement lineage used across later Bubblebacks. Caliber 1030, introduced around 1950, brought a thinner automatic package and a flatter case profile. The family relationship provides context, but individual movement attribution still depends on the movement inside the watch.


The precious-metal-only positioning of the 3131 establishes a template that Rolex returns to later. The Day-Date, launched in 1956 as the first reference offered only in precious metals, is the most famous expression of the same commercial logic: a watch engineered to sell exclusively at the top of the catalog.
The surviving 3131 record is concentrated in precious-metal cases. That material pattern should not be treated as a direct commercial template for later Rolex families.


<span id="collecting-considerations"></span>
<span id="collecting-considerations"></span>
== Collecting considerations ==
== Collecting considerations ==


The 3131 occupies a specific position in the Bubbleback collecting hierarchy. It is less rare than the 1858, less visually dramatic than the engine-turned 3372, and less commercially significant than the 4467 Datejust. It is the first two-piece Bubbleback, and precious-metal-only, which sets a baseline price floor that the broader steel Bubbleback market does not have.
The 3131 is identifiable through its two-piece case, caliber 620 with subsidiary seconds, and the documented gold-case variants. Comparisons with other Bubblebacks depend on material, dial originality, condition and provenance.
 
As with all 1930s–1940s Rolex watches, refinished dials are the norm rather than the exception. An original unrestored dial on a 3131 is scarce and substantially premium-worthy. The grene textured surface, sharp applied gold Arabic numerals, and correct aging of radium lume plots are the three strongest visible indicators of an original dial. Mismatched lume aging between dial and hands is a red flag for at least one component having been replaced. Precious-metal cases also polish much more easily than steel, and 90-year-old gold Bubblebacks have almost universally been polished at some point in their service history. The Phillips 2022 example was described as unpolished, which explains a substantial portion of its above-estimate result.
 
Hallmark verification is required. Case metal is the single largest driver of the watch’s value. A 9K gold 3131 and an 18K gold 3131 are physically similar watches with substantially different retail positions. A seller offering a 3131 in 18K PG or YG should provide clear hallmark photography. Paperwork on 3131-era Rolex watches is effectively non-existent at public auction; a surviving Rolex hangtag (Phillips 2022) or period-correct gold bracelet (Sotheby’s 51699) is unusual and adds meaningful premium, but original boxes from the 1930s–1940s are almost never present.
 
The market sits in roughly the EUR 3,000–5,000 / CHF 3,000–6,000 range for standard-dial, good-condition examples, rising to USD 15,000–20,000 for exceptionally preserved examples with hangtag or bracelet survival. Solid 18K PG examples with pink dials on original bracelets represent the top of the type-specific market; 9K and 14K examples with refinished dials represent the bottom. Between those poles, most 3131 activity happens in the mid-four-figure band.
 
<span id="still-open"></span>
== Still open ==
 
Several questions about the 3131 remain unresolved in the current collector literature.
 
=== Production totals ===
 
No public source documents 3131 production totals. Given the precious-metal-only positioning and the indexed auction frequency, a reasonable inference is that total production was small relative to the contemporary steel Bubblebacks (2940, 2764) that dominate the surviving corpus, but “small” without a number is guesswork.
 
=== 3131 vs 3132 split ===


The sub-seconds 3131 appears slightly more often at auction than the sweep-seconds 3132, but whether this reflects original production ratios or survival bias (sweep-seconds movements with indirect drive may have suffered more service interventions) is not documented.
As with many 1930s–1940s Rolex watches, refinished dials are common. On a 3131, grene texture, sharp applied numerals and matching dial-and-hand lume can support an originality assessment, but none is conclusive alone.


=== Steel production ===
Hallmark verification is required. A 9K gold 3131 and an 18K gold 3131 are physically similar watches, but the metal affects how the lot is described and valued. A seller offering a 3131 in 18K pink or yellow gold should provide clear hallmark photography. Paperwork on 3131-era Rolex watches is uncommon at public auction; the Phillips hangtag and the bracelet described in the Sotheby's 51699 lot are provenance details for those specific watches, not proof of original delivery for every example.


The absence of confirmed steel 3131 examples is suggestive but not conclusive. A single verified steel 3131 would revise the reference’s precious-metal-only characterization. None has surfaced in the indexed auction record, but dealer records and private collections are not indexed systematically.
The auction table records the cited estimates and realised result. Condition, metal, dial originality, hallmarks and provenance should be assessed separately on each watch; the available lots do not support a single market range.


=== End of production ===
== Related references ==


Standard sources place the end of 3131 production somewhere between 1946 and 1948. The 473,634 case (c.1946) is the latest documented example in the indexed auction record, but this is a function of surfaced lots rather than a documented production cutoff.
* [[Reference:2764|Bubbleback 2764]], 1937–1948
* [[Reference:3458|Bubbleback 3458]], 1934–1948
* [[Reference:3065|Bubbleback 3065]], 1937–1950
* [[Reference:2940|Bubbleback 2940]], 1940–1949
* [[Reference:3595|Bubbleback 3595]], 1941–1949
* [[Reference:4467|Bubbleback 4467]], 1945–1949


=== Case construction transition ===
See also the [[Reference:bubbleback|Bubbleback family index]], [[Reference:Movements|movement reference]], [[Reference:Bracelets|bracelet & clasp guide]], and [[Reference:Serial-numbers|serial numbers by year]].


Whether any 1935–1936 transitional examples exist using an intermediate construction is not documented. Forensic comparison of early 3131/3132 cases versus late 3458 cases might reveal transitional steps that the current collector literature does not separate.
<gallery mode="packed" heights="180">
File:Ref_3131_hero.webp|alt=Rolex Bubbleback 3131|Rolex Bubbleback 3131
File:Ref_3131_caseback.webp|alt=Rolex 3131 screw-down caseback|Two-piece Oyster caseback
File:Ref3131_phillips_14k_yg_front.webp|alt=Rolex 3131 in 14K yellow gold, case 412931|14K yellow-gold 3131, Phillips 2022
File:Ref3131_pink_gold.webp|alt=Rolex 3131 in pink gold|Pink-gold 3131
</gallery>


== Sources ==
== Sources ==
* The Vintage Rolex Field Manual, Chevalier Edition — unknown, Morning Tundra
* ''The Vintage Rolex Field Manual'' — Colin A. White, Morning Tundra
* [https://www.phillips.com/detail/rolex/NY080322/64 Phillips NY Watch Auction SEVEN Lot 64 — Rolex ref 3131 14K YG c.1946] — Phillips
* [https://www.phillips.com/detail/rolex/NY080322/64 Phillips NY Watch Auction SEVEN Lot 64 — Rolex ref 3131 14K YG c.1946] — Phillips
* [https://www.sothebys.com/en/buy/auction/2020/watches-online-2/rolex-bubbleback-ref-3131-pink-gold-wristwatch-2 Sotheby's Watches Online — Rolex ref 3131 14K PG c.1946 silvered dial] — Sotheby's
* [https://www.sothebys.com/en/buy/auction/2020/watches-online-2/rolex-bubbleback-ref-3131-pink-gold-wristwatch-2 Sotheby's Watches Online — Rolex ref 3131 14K PG c.1946 silvered dial] — Sotheby's
* [https://www.sothebys.com/en/buy/auction/2020/watches-weekly-geneva-3 Sotheby's Watches Weekly Geneva — Rolex ref 3131 18K PG c.1938 pink dial] — Sotheby's
* [https://www.windvintage.com/rolex-oyster-perpetual-bubbleback-reference-3131 Wind Vintage — Rolex Oyster Perpetual Bubbleback Reference 3131] — Wind Vintage
* [https://www.windvintage.com/rolex-oyster-perpetual-bubbleback-reference-3131 Wind Vintage — Rolex Oyster Perpetual Bubbleback Reference 3131] — Wind Vintage
* [https://www.windvintage.com/blog/how-rolex-became-rolex-the-automatic-perpetual-movement-part-2 Wind Vintage — How Rolex Became Rolex: The Automatic Perpetual Movement Part 2] — Charlie Dunne / Wind Vintage, Wind Vintage
* [https://www.windvintage.com/blog/how-rolex-became-rolex-the-automatic-perpetual-movement-part-2 Wind Vintage — How Rolex Became Rolex: The Automatic Perpetual Movement Part 2] — Charlie Dunne / Wind Vintage, Wind Vintage
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Latest revision as of 05:13, 29 September 2026


Bubbleback › 3131

Rolex Bubbleback 3131
Rolex Bubbleback 3131

The 3131 is an early Rolex Bubbleback with the two-piece Oyster case. Around 1936, the 3131 and its sweep-seconds companion 3132 used a caseback that screws into the case middle, with the bezel formed as part of that middle rather than as a separate ring. Published auction and specialist records show 9K, 14K and 18K yellow- and pink-gold examples. The indexed record contains no confirmed steel 3131.

Core facts

detail value
reference 3131
family Bubbleback (collector name; never official Rolex usage)
production 1936–c.1948 approximate
case diameter 32mm (variously reported as 32.5mm and 33mm; see below)
case shape tonneau
case construction two-piece (caseback screws directly into case middle)
bezel smooth fixed gold, polished
crystal acrylic
movement Cal. 620 (9¾′′′ NA, sub-seconds at 6)
companion reference 3132 (Cal. 630 with centre sweep seconds)
case materials 9K, 14K YG, 14K PG, 18K YG, 18K PG — precious metals only
italian nickname ovetto ("little egg"), per Italian auction usage

Where it sits in the line

The 3131 is an early two-piece Oyster-case Bubbleback.

Earlier Bubblebacks used other case constructions. The 3131 uses a two-piece form that appears across later Bubbleback references, although details still vary by reference and period.

Within its run, surviving 3131 examples show variation in dials, hands, case metals and retailer signatures. The 3131 and 3132 were companion references: the 3131 has subsidiary seconds, while the 3132 uses an indirect centre-seconds drive. Auction frequency is not a reliable measure of original production or survival, so the page does not infer a ratio.

The transition it completes

The references before 3131 establish the early Oyster Perpetual and its automatic rotor. The 3131 and 3132 then document the two-piece case form that becomes common among later Bubblebacks. That is a useful case-history marker, but surviving examples do not prove that later Oysters used identical construction.

The 3131 falls in the pre-war and wartime Bubbleback period. Its surviving variants are best described through case, movement, dial and hallmark evidence rather than through an assumed production strategy.

The two-piece case

The defining technical feature of the 3131 is its case construction. On the earlier first-generation Bubbleback architecture, the bezel, mid-case, movement-holder ring and caseback combined as distinct parts to make the sealed Oyster unit. The two-piece case eliminates the internal ring. The bezel is integral to the mid-case, with the lugs, crystal seat and outer profile formed as one component. The caseback screws directly into threads cut into the mid-case.

The two-piece form reduces the number of sealing surfaces and makes the case thinner. Because the bezel is part of the mid-case, damage to one component affects the other.

The 3131 case carries the Oyster Watch Co. signature on the caseback interior along with period-correct patent markings and hallmarks. Reference numbers between the lugs are not standard on the published 3131 examples; the reference is often engraved on the caseback interior, consistent with pre-1948 practice. Serials appear between the lugs at 6 o'clock on documented examples.

  • Rolex 3131 caseback
    Rolex 3131 screw-down caseback
  • Rolex 3131 in 14K yellow gold, case 412931 (Phillips NY 2022, sold USD 18,900).
    Rolex 3131 in 14K yellow gold, case 412931 (Phillips NY 2022, sold USD 18,900).
  • The 3131's bubble caseback, screwing directly into the case middle.
    The 3131's bubble caseback, screwing directly into the case middle.

Dimensions

Case diameter is reported variously as 32mm, 32.5mm and 33mm. The measurement point matters on a tonneau case; Phillips records 32mm for its 1946 example. The domed caseback contributes more to the watch’s profile than the small differences in diameter. Caliber 620 and its rotor require that clearance, but surviving cases should be measured individually.

The Cal. 620

Cal. 620 is a 9¾′′′ automatic movement commonly listed with 17 jewels and an 18,000 bph frequency. Published sources give different reserve figures, so the running time belongs to the serviced movement rather than to a fixed reference specification. The caseback dome contributes substantially to the profile.

Cal. 620 follows the earlier 520 family. Its rotor and winding layout are part of the reason the Bubbleback case needs additional clearance, but a case profile alone does not establish a particular movement revision.

Cal. 620 is unidirectional: the rotor spins freely in one direction and winds in the other. True bidirectional winding in a Rolex movement arrives only with Cal. 1030 in 1950, which is also the movement that ends the Bubbleback era by enabling a thin flat caseback.

Caliber 620 belongs to the Aegler-built Rolex movement lineage. Corporate ownership, design authorship and manufacturing responsibility changed over time; the article does not use “in-house” as a shorthand for all three.

On the 3131, Cal. 620 drives subsidiary seconds at 6 o'clock. The companion 3132 used Cal. 630, a related movement with an indirect drive for centre sweep seconds. The two references should be distinguished by the movement and dial layout, not by an assumed price or buyer preference.

Precious metals only

The documented 3131 record is concentrated in precious metals. Auction and specialist examples include 9K, 14K and 18K yellow- and pink-gold cases. The indexed examples are precious metal; that surviving record is not a production census.

The best-documented 14K yellow gold example is the Phillips NY Watch Auction SEVEN 2022 lot (case 412931, c.1946), sold with its original Rolex hangtag, an unusual survival on a watch approaching 80 years old.

14K pink gold is the Sotheby's Watches Online 2020 configuration (case 473634, c.1946, silvered dial). The alloy differs from 18K pink gold, and the cited examples include North American-market watches.

18K yellow-gold examples appear in auction and dealer listings. Assay marks vary with the market of sale, so the caseback and lugs need to be read on each watch.

An 18K pink-gold example appears in the Sotheby's Watches Weekly Geneva 2020 record (case 51699, c.1938, pink dial). The catalogue describes its bracelet; original delivery still needs watch-specific proof.

9K gold examples are associated with British-market watches in the specialist record. The alloy and hallmark should be verified from the case; a dealer listing alone does not establish the intended sales market or an original price position.

The indexed sources contain no confirmed stainless-steel 3131. That absence does not prove that no other material variant was made.

Rolex 3131 in pink gold, one of several documented precious-metal variants.
Rolex 3131 in pink gold, one of several documented precious-metal variants.

The suffix system

The Vintage Rolex Field Manual's Bubbleback suffix system applies to the 3131. Within the precious-metal-only corpus, the relevant variants are:

  • 3131/7 — solid gold (yellow or rose; color not encoded in the suffix)
  • 3131/8 — alternate solid gold (typically used to distinguish karat, e.g. 14K vs 18K)

The suffix codes were period-authentic (Rolex used them internally on parts lists and service paperwork c.1933–1953) but were rarely engraved on casebacks. Most surviving 3131 casebacks carry only the four-digit "3131" without the slash variant. The suffix must be inferred from the hallmarks and dial rather than read off the case directly. A seller claiming a specific /7 or /8 variant without hallmark documentation should be treated cautiously.

Dial and hand variants

The 3131 record shows white and silvered dials, often with applied gold Arabic numerals and subsidiary seconds at 6. Cream and ivory dials also appear. Pink and salmon dials are documented on some pink-gold cases, including the Sotheby's Watches Weekly 2020 example (case 51699). Retailer signatures and dial finishing vary by surviving watch.

Beige and silvered dials are common in the published record. Black dials and grene-textured dials need close inspection because refinishing and later dial work are common on watches of this age; texture alone does not prove originality.

Published examples show pencil, feuille and spade hand forms. Luminous material and patina should be assessed from the individual hands and dial; hand style alone does not establish a production date.

Auction and market record

The cited auction record contains one realised Phillips result and two Sotheby's estimates. These lots show documented examples, not a complete market series.

Venue Date Lot Case No Material Dial Notes Result
Phillips NY (Watch Auction SEVEN) 2022 64 412931 14K YG — c.1946, movement 20915, unpolished, original Rolex hangtag USD 18,900 (est USD 8k–16k)
Sotheby's Watches Online 2020 — 473634 14K PG Silvered c.1946 est CHF 5,000–7,000
Sotheby's Watches Weekly Geneva 2020 — 51699 18K PG Pink c.1938, on original Rolex bracelet est CHF 4,000–6,000

The Phillips NY 2022 lot was a 14K yellow-gold 3131 that sold for USD 18,900 against an estimate of USD 8,000–16,000. The catalogue records an original Rolex hangtag with a handwritten serial number. That accessory is part of the lot’s provenance; it does not establish a general premium for every 3131.

The two Sotheby's 2020 lots were estimated in the CHF 4,000–7,000 and CHF 4,000–6,000 ranges shown in the table. Those estimates should be read with the lot descriptions and condition; they are not a general valuation band.

Case number observations

The three documented cases span roughly 51,699 (c.1938) through 473,634 (c.1946), a range consistent with the broad 1936–1948 dating used by the family guide. The sample is too small to infer production batches. The indexed auction record contains no confirmed post-1948 example; that absence does not establish an end date.

The reference is generally placed in the late-1930s and 1940s Bubbleback period. Later two-piece references, including 3065, 3372, 4220 and early 4467 examples, overlap the same broad era. Exact production totals and a precise replacement date are not documented in the cited sources.

Place in Bubbleback history

The 3131 records two early Rolex design developments: the two-piece Oyster case and the 620-family automatic movement.

The two-piece Oyster case appears across many later Bubbleback references, including 2940, 2764 and 3065. The exact case, bezel and movement details still need to be checked by reference; this page uses the 3131 as an early dated example of the form.

Cal. 620 sits in the 620/630/635/645 movement lineage used across later Bubblebacks. Caliber 1030, introduced around 1950, brought a thinner automatic package and a flatter case profile. The family relationship provides context, but individual movement attribution still depends on the movement inside the watch.

The surviving 3131 record is concentrated in precious-metal cases. That material pattern should not be treated as a direct commercial template for later Rolex families.

Collecting considerations

The 3131 is identifiable through its two-piece case, caliber 620 with subsidiary seconds, and the documented gold-case variants. Comparisons with other Bubblebacks depend on material, dial originality, condition and provenance.

As with many 1930s–1940s Rolex watches, refinished dials are common. On a 3131, grene texture, sharp applied numerals and matching dial-and-hand lume can support an originality assessment, but none is conclusive alone.

Hallmark verification is required. A 9K gold 3131 and an 18K gold 3131 are physically similar watches, but the metal affects how the lot is described and valued. A seller offering a 3131 in 18K pink or yellow gold should provide clear hallmark photography. Paperwork on 3131-era Rolex watches is uncommon at public auction; the Phillips hangtag and the bracelet described in the Sotheby's 51699 lot are provenance details for those specific watches, not proof of original delivery for every example.

The auction table records the cited estimates and realised result. Condition, metal, dial originality, hallmarks and provenance should be assessed separately on each watch; the available lots do not support a single market range.

Related references

See also the Bubbleback family index, movement reference, bracelet & clasp guide, and serial numbers by year.

  • Rolex Bubbleback 3131
    Rolex Bubbleback 3131
  • Rolex 3131 screw-down caseback
    Two-piece Oyster caseback
  • Rolex 3131 in 14K yellow gold, case 412931
    14K yellow-gold 3131, Phillips 2022
  • Rolex 3131 in pink gold
    Pink-gold 3131

Sources

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