Rolexopedia

Rolex 3131 Bubbleback

This is a checked version, approved on 21 September 2026. New changes may have been made.


Bubbleback › 3131

Rolex Bubbleback 3131
Rolex Bubbleback 3131

The 3131 is one of the first Rolex Bubblebacks 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; no confirmed steel 3131 is cited here.

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 no ratio is stated here.

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 belongs to the mature 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 gains are easy to see: a thinner case, fewer sealing surfaces, easier service, and simpler production. The trade-off is just as clear: because the bezel is the mid-case, damage to one means damage to both.

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.

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    Rolex 3131 screw-down caseback
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    Rolex 3131 in 14K yellow gold, case 412931 (Phillips NY 2022, sold USD 18,900).
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    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. No confirmed stainless-steel 3131 is cited here, but the 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 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.

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.

No confirmed stainless-steel 3131 has surfaced in the sources used here. That absence does not prove that no other material variant was made.

 
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. No confirmed 3131 example post-1948 appears in the indexed auction record, but auction absence is not proof of 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 sources used here.

Why the reference matters

The 3131 is useful for tracing two early Rolex design threads: 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 is useful 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.

Gallery

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    Rolex Bubbleback 3131
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    Two-piece Oyster caseback
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    14K yellow-gold 3131, Phillips 2022
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    Pink-gold 3131

Sources

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