Reference:2940
Bubbleback → 2940
The 2940 is the wartime Bubbleback. Introduced around 1940 and produced through 1949, it spans the years when Swiss watch production had to keep running while Europe burned, and the commercial catalog had to keep selling while most of its traditional markets closed. Rolex met the moment with a two-piece Oyster that kept to the form the 3131 established four years earlier but pushed it toward volume production in steel. Where the 3131 was a precious-metal statement reference, the 2940 was the version that went to war. It came in stainless steel, with center sweep seconds and a dial catalog wide enough to suit whatever market still took delivery. It is also the reference that sits at the center of the “hooded lug” forgery problem that continues to haunt Bubbleback authentication.
Core facts
| detail | value |
|---|---|
| reference | 2940 |
| family | Bubbleback (collector name; never official Rolex usage) |
| production | c.1940–1949 (peak 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 the volume wartime Bubbleback. The 3131 and its sweep-seconds twin 3132 had proven in 1936 that the two-piece Oyster could be manufactured at scale; the 2940 is the reference that made the same case architecture available in steel and inexpensive gold cap. It carries the sweep-seconds configuration that the 3132 pioneered, a center-mounted seconds hand running off Cal. 9¾’’’ rather than a subsidiary register at 6, and pairs it with a case sized for a masculine wartime wrist. Production runs from roughly 1940 through 1949, with the concentrated peak falling in the five years from 1942 through 1947.
Within the broader Bubbleback family, the 2940 sits alongside the sub-seconds 2764, the steel-and-precious 3065 with its hooded lugs, and the 3372 with its engine-turned bezel. Steel 2940s carry the most examples; the 14K gold-top/steel configuration sits above them in the hierarchy, with solid 9K gold examples the scarcest of the three materials. Earliest surfaced serials run in the low 200,000s, consistent with 1942 production; the latest documented examples push into the high 600,000s, consistent with 1949. The reference does not evolve in generational tiers the way a later Submariner does. Variation happens in dials, hands, and the metal the case was cut from.
The wartime commercial position
The early 1940s were an unusual commercial window for Rolex. Switzerland’s neutrality kept production running through a period when most other European watchmakers were either shuttered or converted to military work. German and Italian markets closed; Allied markets opened unevenly. Rolex responded by pushing export into the markets that remained: the UK (which took solid 9K gold and gold-top/steel Bubblebacks in volume), neutral-nation retailers, and later the US through increasing wartime American interest. The 2940’s dial variety tracks that commercial spread. Sector dials, California dials, Arabic-radium dials, 24-hour military dials, and retailer-signed dials all surface on 2940 cases, and that breadth is not typical for a single reference in a single decade. It reflects Rolex’s willingness to configure a Bubbleback however a given retailer or market wanted it.
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. No separate bezel ring. No discrete movement-holder. The case 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 key reference point for the hooded-lug authentication problem that the reference carries.
The hooded-lug debate
A certain number of 2940s surface in dealer listings with hooded lugs, extended “teardrop” lug profiles that sweep down and around the case to cover the spring bar area. Hooded-lug Bubblebacks are a documented Rolex configuration, but they are properly the province of ref 3065, not ref 2940. The VRF collector consensus, echoed on TimeZone, RolexForums, and specialist forum threads, is that 2940s appearing with hooded lugs are almost invariably aftermarket modifications. A 2940 case is extended with welded or resoldered lug material to impersonate the rarer and more commercially desirable 3065. The authentication points are caseback stamping (which should read 2940, not 3065, on a genuine 2940), the precise geometry of the lug-to-case transition (which reveals tool marks on modified examples), and the proportions of the hood itself relative to the case middle. Dealer listings on 1stDibs and comparable platforms occasionally present 2940/hooded-lug examples as authentic; the specialist collector literature does not accept them.
When a 2940 appears for sale with hooded lugs, the presumption is modification. The burden is on the seller to demonstrate otherwise, and the published collector record does not contain a documented example where that demonstration has succeeded.
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 9¾’’’ automatic caliber family, with 17 jewels in most documented examples and 18 jewels cited occasionally by sources that appear to refer to higher-grade or service-replacement variants. The base movement is an evolution of Cal. 620 with the indirect-drive sweep seconds mechanism that characterizes Cal. 630. It runs at 18,000 beats per hour, carries a straight-line lever escapement, a Breguet-style hairspring, and shock protection in the later production examples. The plating is rhodium, standard for the era. Winding is automatic and unidirectional through the 360-degree rotor. The rotor spins freely in one direction and engages the winding gear in the other, which is what gives the Bubbleback its case-back dome.
The 2940’s movement is non-hacking. Pulling the crown to the setting position stops the hands from advancing but the seconds continue to sweep; setting to the exact second requires a fractional backlash adjustment that is second nature on contemporary vintage Rolex but foreign to any Rolex made after the introduction of hacking seconds in the 1970s.
Cal. 630 is cited on some 2940 examples and is the formal numbered caliber for the 9¾’’’ sweep-seconds configuration. The two designations refer to the same movement family under different naming conventions. The ligne measurement (9¾’’‘) is older, and the numbered caliber (630) is the catalog reference Rolex used in service documentation. A 2940 described with Cal. 9¾’’’ and a 2940 described with Cal. 630 are, in practice, the same watch.
Dial variants
The 2940 carries the widest dial catalog of any Bubbleback reference. 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, is rare on the 2940. The sector dial is one of the signature 1940s Rolex dial configurations and surfaces occasionally on 2940 cases, where it carries a significant premium over the standard silvered or black dial.
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. The Phillips Geneva Watch Auction TWO 2015 Lot 277 example is the best-documented original-production California 2940: 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. Original-production California dials on 2940 cases are scarce; refinished California dials on 2940s are common and trade at substantial discounts to confirmed original examples.
The most commonly encountered 2940 dial is the Arabic radium, with hour markers filled with radium luminous compound on a silvered or black base. Original radium fill has aged to a warm orange-brown patina on surviving examples; white or cream lume on a 2940 dial is almost always a refinish indicator.
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.
Salmon is the rarer still. The Heritage Auctions “Two Tone Salmon Dial” example, a c.1942 2940 with a salmon-finish dial, is the best-documented example in the public auction record. Salmon dials on 2940 cases are scarce enough that any appearance at auction or dealer inventory draws collector attention disproportionate to the reference’s general market position.
Silvered and champagne-finish dials with applied hour markers and a minute track represent the baseline dress-watch configuration for 2940s sold to retailers who did not specify a more unusual dial treatment. These are the most commonly surfaced dial type in dealer inventory.
Black lacquer or matte black dials run against the dominant dial language of the era. Original black-dial 2940s are scarce; the configuration is more commonly encountered as a refinish applied to a case whose original dial had degraded beyond reuse.
The 24-hour military dial is the most unusual 2940 variant, with hour markers running 1 through 24 rather than 1 through 12. It surfaces on a small number of cases, typically in connection with military or specialized-use procurement, and any example at auction commands a substantial premium over standard-dial prices.
Dealer-signed dials surface on 2940s more frequently than on most later Rolex references, reflecting the 1940s practice of retailers commissioning co-signed dials for their own stock. 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 configurations appear across the surviving 2940 corpus. Mercedes-style blued hands with luminous fill (the hour hand terminating in the circular Mercedes motif) surface on 1942 examples and predate the later standardization of Mercedes hands on the Submariner and Explorer lines. Sword luminous hands, broader and more tapered than the Mercedes style, appear on a range of 1940s 2940s. Pencil hands with radium fill are the most commonly encountered configuration and match the baseline Arabic radium dial layout. Dauphine hands, the faceted triangular hand shape more typical of dress watches, appear on silvered and champagne dial examples where the intent was a formal rather than sporting presentation.
Mismatched lume aging between dial markers and hands is the single most reliable indicator of hand replacement. On a 2940 whose dial lume has aged to orange-brown, hands with cleaner or differently-patinated lume suggest a service replacement; the two components should age in parallel if both are original.
Case materials
Three case materials appear in the 2940 corpus.
Stainless steel is the most commonly encountered. The 2940 was Rolex’s workhorse steel Bubbleback of the wartime period, and steel examples constitute the bulk of the surviving population. The Phillips 2015 Lot 277 example is steel; so are the majority of dealer inventory listings across 1stDibs, Chrono24, and specialist vintage dealers.
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 2940s sit in dealer inventory at a modest premium over comparable steel examples and were particularly common in the US and UK export markets.
9K solid gold is the scarcest. The 9K gold configuration (permitted for hallmarking in the UK but not most continental European markets) was the British Commonwealth market option and carries British assay marks on the caseback and lugs. 9K gold 2940s appear less frequently than either steel or gold-top/steel examples and trade at a premium that reflects both their scarcity and their precious-metal positioning, though below the price a comparable 14K or 18K gold 3131 would command.
No 18K gold 2940 has surfaced in the indexed auction record. The absence is not conclusive; dealer and private records are not systematically indexed. But the 2940 appears to have been positioned as a steel, gold-top, and 9K gold reference rather than a premium solid gold one. The 3131 and its precious-metal siblings occupied that position in the catalog.
The Zell Bros Turtle variant
The 2940 carries one documented retailer-specific variant that sits outside the standard dial catalog: the “Turtle Perpetual Timer” sold through Zell Bros, an Oregon-based jewelry retailer, with its own dial signature and a market-specific commercial name. The Turtle designation was Zell Bros’ retail branding rather than a Rolex designation, and the watches are standard 2940 cases with the Zell Bros dial treatment. The configuration is sufficiently documented that “Zell Bros Turtle” is a recognized 2940 sub-variant in the collector literature, and surviving examples trade at a premium over standard-dial 2940s reflecting both the retailer-signed dial and the named-variant collector interest.
The Turtle example is one of several mid-century US retailer variants where a jewelry chain contracted with Rolex for signed-dial stock and gave the resulting watches retail-specific names. The practice was more common on 1940s and 1950s Rolex production than it is on any modern reference; the Zell Bros Turtle is the 2940’s best-known example.
Auction and market record
Two public auction lots anchor the documented 2940 market picture, supplemented by dealer inventory data.
| 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 | — | — | — | Two-tone salmon | c.1942 | — |
The Phillips 2015 result is the headline data point. A steel 2940 with a pink California dial sold at CHF 10,000 on an estimate of CHF 8,000–12,000, a market-range result for the configuration, with the California dial driving the estimate above what a standard Arabic-radium 2940 would command. The Heritage salmon-dial example is less completely documented in the public record but establishes the salmon dial as a documented configuration at auction-house level rather than a dealer-listing curiosity.
Dealer market data for the period 2020–2026 places the reference in a specific price band. Average private-sale pricing sits at roughly USD 2,352, with dealer pricing at an average of USD 3,455, the dealer premium reflecting both retail margin and the dealer market’s tendency to carry better-condition or more complete examples. The broader price range runs from USD 2,860 at the bottom to USD 11,950 at the top, with the upper figure reflecting rare dial configurations (salmon, sector, 24-hour military), exceptional condition, or precious-metal cases. Five-year market change sits at roughly +36.2 percent, consistent with broader vintage Rolex appreciation over the same period but below the ten-year appreciation that a comparable Submariner or GMT-Master has delivered.
The 2940 sits in the accessible middle of the Bubbleback market. It is not as visually dramatic as the engine-turned 3372. It does not sit at the hinge of history the way the 3131 does, or at the rarity end where the 1858 sits. It is less metal-premium than a solid 18K gold 3131. What the 2940 offers is a wartime Rolex at a sub-USD-5,000 entry point in standard steel configuration, with clear paths to higher price tiers for better dials, better condition, and precious-metal cases. The market reflects that positioning.
Serial range observations
The documented 2940 serial range runs from approximately 200,000 (c.1942) through approximately 690,000 (c.1949). The range is consistent with the 1940–1949 production window inferred from the surviving corpus, though the earliest serials in the low 200,000s suggest that production may not have begun in earnest until 1942 rather than 1940. The first two years of the nominal window may have been a slow ramp-up or a production-overlap period with earlier references. The 1949 end of production coincides with the transition toward the references that would define the early 1950s Bubbleback era (4220, 4467, and the 4777/5015 pairings) as the two-piece case itself began to give way to the thinner Cal. 1030–powered watches.
Collecting considerations
The 2940 is a reference where dial configuration drives value more decisively than case material or condition alone. A standard Arabic-radium steel 2940 in good unrestored condition trades in the low-to-mid four figures. A California-dial steel 2940, in comparable condition, trades at roughly double that. A salmon or sector dial example can push to the top of the reference’s documented range. A 24-hour military 2940 surfaces rarely enough that price discovery happens case by case. The dial catalog is the first item of diligence on any 2940 purchase.
Original-dial diligence is non-trivial. Refinished dials outnumber original dials in the surviving population. Eight decades of service activity have given plenty of opportunity for radium replacement, re-lacquering, and full refinishes, and the refinishing industry in the mid-to-late twentieth century was proficient enough that a well-executed refinish can be difficult to detect. The indicators that matter: radium patina matching between dial and hands, printing sharpness consistent with 1940s-era dial manufacturing, correct font choices for the era (which refinishers often subtly miss), and the absence of refinisher signatures or marks on the dial back. Provenance documentation (auction-house lot photography, extract from Rolex archives for later references, retailer paperwork) helps but is rare for 2940s.
Hooded-lug skepticism is required. Any 2940 offered with hooded lugs should be presumed an aftermarket modification until demonstrated otherwise, and the demonstration requires more than seller assertion. A seller who cannot produce either clear between-lug stamping showing the unchanged 2940 reference or professional authentication from a recognized vintage Rolex specialist has effectively not made the case. The reference’s authentic configuration is squared-off inner lugs; that is the baseline against which any deviation must be justified.
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 non-negotiable on any precious-metal listing. Cases that have been replated, regilded, or otherwise worked should be identified as such, and the premium a solid gold case commands should survive the verification step to be worth paying.
The 2940 trades primarily through specialist dealer inventory and the secondary auction market rather than at major Geneva houses. Phillips and Heritage have handled examples; Sotheby’s and Christie’s have occasionally included 2940s in mid-tier vintage lots; Antiquorum and Bonhams have listed them in catalog sales. The bulk of market activity happens through vintage Rolex specialist dealers, forum-adjacent private sales, and platforms like Chrono24 and 1stDibs. Price discovery is accordingly uneven, and a given configuration can trade at widely varying prices depending on venue and market conditions.
Still open
Several questions about the 2940 remain unresolved in the current collector literature.
Total production
No public source documents 2940 production totals. The serial-range inference from ~200,000 to ~690,000 covers a ~490,000-unit span, but serial numbers in this period were not reference-specific. They covered the entire Rolex production of the year, so the actual 2940 share of that range is not documented.
1940–1941 production
The earliest surfaced 2940 serials run in the low 200,000s, consistent with 1942 production. Whether any 2940s were produced before 1942 in non-trivial volume, or whether the reference was introduced on paper in 1940 but not pushed to volume production until 1942, is not documented.
Hooded-lug authenticity
The collector consensus is that hooded-lug 2940s are aftermarket modifications. A single rigorously authenticated hooded 2940 (with period-correct stamping, consistent lug geometry, and provenance from a dealer or auction house whose authentication standards are accepted in the specialist community) would revise this position. None has surfaced in the indexed record.
Caliber grade variation
Some 2940s are documented with 17-jewel movements, others with 18 jewels. Whether this reflects original production grade differences, service-era movement variants, or documentation inconsistency across sources is not established.
Dial configuration totals
The dial catalog (sector, California, Arabic radium, two-tone, salmon, black, 24-hour military, silvered, champagne, dealer-signed) is well-attested across surviving examples, but no public source documents relative production volumes. The rarity claims in the collector literature (“salmon is rare,” “24-hour military is very rare”) are inferred from auction and dealer frequency rather than documented against production records.
Sources
- The Vintage Rolex Field Manual, Chevalier Edition — unknown, Morning Tundra
- Phillips — geneva two 2015 lot277
- Heritage Auctions — 2940 salmon
- Bob's Watches — Rolex Bubble Back Collector's Guide — Bob's Watches
- swisswatchexpo bubbleback
- WatchUSeek — 2940 threads
- Vintage Rolex Forum — 2940 hooded debate
- 1stDibs — 2940 listings
- Rolex Forums — 2940
- Caliber Corner — 630