Rolex 2940 Bubbleback
Bubbleback › 2940
The 2940 is a 31–32mm two-piece Bubbleback with center seconds. Published examples include stainless-steel, gold-top and 9K cases, with dial variants documented across 1940s auction and specialist records.
Core facts
| detail | value |
|---|---|
| reference | 2940 |
| family | Bubbleback (collector name; never official Rolex usage) |
| production | c.1940–1949; many cited examples date to 1942–1947 |
| case diameter | 31–32mm |
| case shape | round |
| case construction | two-piece (caseback screws directly into case middle) |
| lug-to-lug | ~38–38.5mm |
| lug width | 16–17mm |
| lugs | squared-off inner profile (hooded examples debated) |
| bezel | smooth, polished, domed |
| crystal | acrylic |
| seconds | center sweep (not sub-seconds) |
| movement | Cal. 9¾′′′, 17 jewels (some 18j); some examples Cal. 630 |
| case materials | stainless steel, 14K gold-top/steel, 9K solid gold |
| serial range | ~200,000 (c.1942) to ~690,000 (c.1949) |
Where it sits in the line
The 2940 is a center-seconds Bubbleback that followed the two-piece case introduced by the 3131 and 3132. Its center-mounted seconds hand runs from the 9¾′′′ movement family rather than a subsidiary register at 6. Published records place production roughly from 1940 through 1949, with many cited examples dated 1942–1947.
Within the Bubbleback range, the 2940 sits beside the sub-seconds 2764, the more mixed-metal 3065, and the engine-turned 3372. Steel, gold-top over steel, and 9K solid-gold cases are documented; the cited records do not establish production proportions. The documented serial range runs from the low 200,000s to the high 600,000s, which fits roughly 1942 to 1949. Unlike later sports references, the 2940 does not break into neat generations. The variation is in dials, hands, and case metal.
The wartime commercial position
The early 1940s records show the 2940 in more than one market. Dial and case combinations vary across the surviving examples, but the cited sources do not establish how Rolex allocated production by market.
The two-piece case
The 2940 uses the two-piece case architecture the 3131 introduced in 1936: a round mid-case with the bezel integral to the case middle, closed at the back by a screw-down caseback that threads directly into the case. The case has no separate bezel ring or discrete movement-holder. It measures 31–32mm in diameter with a lug-to-lug of roughly 38–38.5mm and a lug width between 16 and 17mm. The bezel is smooth and domed, polished, unmarked, set slightly proud of the crystal aperture.
The inner lug profile is squared-off. This is the standard 2940 lug configuration, and it is the reference point for checking a hooded-lug claim.
The hooded-lug debate
Published Bubbleback references associate the hooded-lug case form with the 3065 rather than the 2940. A 2940 offered with hooded lugs therefore needs close comparison of caseback stamping, lug geometry and provenance before the reference is accepted.
A hooded-lug 2940 claim needs positive evidence. The cited collector record does not establish a confirmed original 2940 with that case form.
Serial and reference engraving
2940 cases carry the reference number engraved between the upper lugs and the serial number engraved between the lower lugs, consistent with the 1920s–1940s Oyster convention. Caseback interiors carry the Oyster Watch Co. signature along with period-correct patent and hallmark markings. The reference is also repeated on the caseback interior. This double-engraving of the reference makes 2940 authentication relatively straightforward where the lugs have not been altered; forged-hood examples can be detected by comparing the between-lug engraving (still typically legible as 2940) against the lug profile (incorrectly modified to a hooded form).
The movement
The 2940 runs on Rolex's 9 3/4 ligne automatic family, usually 17 jewels and sometimes 18 in better-grade or later-service examples. The practical point is simple: this is a Bubbleback-era automatic with center sweep seconds, not a special one-off movement.
The cited 2940 movements do not have a documented hacking feature. Pulling the crown stops the hands while the seconds continue to run, so exact synchronization requires a small setting correction.
Cal. 630 is cited on some 2940 examples as the numbered designation for the 9¾′′′ sweep-seconds configuration. Other catalogues give only the ligne measurement. The movement and its markings should be inspected on each watch rather than inferred from the reference alone.
Dial variants
The 2940 has a broad documented dial range. Some of this breadth reflects Rolex's pre-war practice of configuring dials to retailer specification; some of it reflects the reference's long production run across multiple export markets; some of it reflects refinishing activity over the subsequent eight decades.
The sector dial, multi-tone silver with dot and Arabic indices divided into concentric or radial zones, appears less often in the cited 2940 record. The sector layout appears on some 2940 cases; the cited auction record does not establish a general price premium.
The California dial, Roman numerals on the upper half and Arabic numerals on the lower half with a square marker at 6, appears on the 2940 both as original Rolex production and as later refinishing. Phillips Geneva Watch Auction TWO 2015 lot 277 is a documented original-production California 2940 example: stainless steel case, pink California dial, dated c.1941, estimated CHF 8,000–12,000 and sold at CHF 10,000 on the low estimate. Originality is difficult to establish because refinished California dials also circulate; the lot record should be checked against the individual dial.
Arabic-radium dials are documented on silvered and black bases, with hour markers filled with radium luminous compound. Original radium fill has aged to a warm orange-brown patina on surviving examples; white or cream lume on a 2940 dial needs inspection for refinishing or later replacement.
Two-tone contrasting-zone dials divide the dial into inner and outer zones with contrasting finishes, typically a silver outer zone with a darker inner track or vice versa. The two-tone layout traveled across several contemporaneous references and appears on the 2940 in examples dated to 1942 and the surrounding years.
Heritage Auctions catalogued a c.1942 two-tone salmon 2940. That lot documents the configuration; it does not establish production frequency or a general market premium.
Silvered and champagne-finish dials with applied hour markers and a minute track are also documented. Dealer listings are not a controlled measure of their share of production.
Black lacquer or matte black dials run against the dominant dial language of the era. Black-dial 2940s appear in the record, alongside refinished examples. Dial originality requires watch-specific inspection.
A 24-hour dial with markers from 1 through 24 is reported on a small number of 2940 cases. The cited material does not establish its procurement history or a general price premium.
Dealer-signed dials are documented on 2940 examples. The Erbe Basel signature is one recorded case; the cited sources do not establish how common retailer commissions were across the reference. The "Erbe Basel" signature, for the Erbe jewelry retailer in Basel, Switzerland, is one of the documented dealer signatures on 2940 dials.
Hand variants
Four hand styles are documented on surviving 2940s: Mercedes, sword, pencil, and dauphine. The hand set should be assessed with the dial, case, and movement.
Mismatched lume aging between dial markers and hands is one warning sign of a possible hand replacement. On a 2940 whose dial lume has aged to orange-brown, hands with cleaner or differently patinated lume need comparison with the dial, case history, and service record.
Case materials
Three case materials appear in the 2940 corpus.
Stainless-steel examples are documented in the Phillips lot and dealer records. Those listings do not establish the material proportions of the original production run.
14K gold-top over steel is the mid-tier configuration. A gold-top case carries a solid gold bezel and top-side of the mid-case with a steel caseback and internal structure. The gold appears on the visible surfaces without the cost of a fully solid gold case. 14K gold-top/steel examples are documented in dealer and auction records; the cited material does not establish a production share or universal price difference.
9K solid-gold examples are documented with British assay marks in the cited material. The available records do not establish their production share or a universal price relationship with steel or gold-top cases.
No 18K gold 2940 appears in the indexed auction record. That absence is not conclusive, and the available records do not define a complete material catalogue.
The Zell Bros Turtle variant
The Zell Bros “Turtle Perpetual Timer” is a documented retailer-signed 2940 branch. The watch remains a 2940, with the name and dial signature recorded as part of the individual configuration.
The Turtle fits the broader record of retailer-signed Rolex dials in the mid-century US market. The cited sources do not establish how many such 2940s were made.
Auction and market record
The public auction record cited on this page contains a Phillips California-dial lot and a Heritage salmon-dial lot.
| Venue | Date | Lot | Material | Dial | Notes | Result |
|---|---|---|---|---|---|---|
| Phillips Geneva Watch Auction TWO | 2015-05-09 | 277 | SS | Pink California | c.1941 | CHF 10,000 (est CHF 8,000–12,000) |
| Heritage Auctions | n/a | n/a | n/a | Two-tone salmon | c.1942 | n/a |
Phillips lot 277 was a steel 2940 with a pink California dial. It sold for CHF 10,000 against an estimate of CHF 8,000–12,000. The result belongs to that lot and configuration. Heritage’s salmon-dial lot documents that configuration at auction; its available record is less complete than the Phillips lot.
Dealer listings are not a controlled market series. They should be kept separate from the two cited auction lots when assessing an individual watch.
The cited examples differ in case, movement and dial configuration. Auction results remain tied to each watch's condition, originality, metal and provenance.
Serial range observations
The documented 2940 serial range runs roughly from the low 200,000s into the high 600,000s, which is enough to place examples into a wartime or late-run band even if it does not give exact factory dating.
Collecting considerations
Dial configuration is a major part of assessing a 2940, but the cited lots do not support a general price range. Check the dial, lume, hands, case material and provenance together.
Original-dial diligence on the 2940 is hard. Refinished dials are common, so radium matching, print quality, correct fonts, and any surviving provenance matter a lot more here than they do on easier later references.
A 2940 offered with hooded lugs needs clear between-lug 2940 stamping, case geometry and specialist authentication before its configuration is accepted. The documented standard configuration has squared-off inner lugs.
Case material verification matters at the high end of the market. 14K gold-top/steel and 9K solid gold examples carry substantially different value positions from steel 2940s, and hallmark photography is necessary when assessing a precious-metal listing. Cases that have been replated, regilded, or otherwise worked should be identified as such, and any value comparison should follow verification of the case material.
The cited record is concentrated in specialist and auction listings. Results from different venues are not directly comparable, so each lot should be read with its condition and provenance details.
Related references
- Bubbleback 3595 (1941–1949)
- Bubbleback 3065 (1937–1950)
- Bubbleback 2764 (1937–1948)
- Bubbleback 3131 (1936–1948)
- Bubbleback 4467 (1945–1949)
- Bubbleback 3458 (1934–1948)
See also the Bubbleback family index, movement reference, bracelet & clasp guide, and serial numbers by year.
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1942 stainless-steel 2940 -
Rose-numeral dial example -
Bubbleback case profile -
Center-seconds dial detail
Sources
- The Vintage Rolex Field Manual — Colin A. White, Morning Tundra
- Phillips Geneva Watch Auction TWO, lot 277, Rolex 2940 California dial — Phillips
- Heritage Auctions, two-tone salmon dial Bubbleback ref. 2940, lot 54176
- Bob's Watches — Rolex Bubble Back Collector's Guide — Bob's Watches
- swisswatchexpo bubbleback
- WatchUSeek — 2940 discussion threads used as collector leads
- Vintage Rolex Forum — 2940 hooded debate
- 1stDibs — 2940 listings
- Rolex Forums, “Another Bubbleback question” — reference 2940 engraving discussion
- Rolex Oyster Story: “At one with the movement”; Rolex, 1931 Perpetual rotor history
- Caliber Corner — 630