Reference:2940

Bubbleback -> 2940

1942 steel Bubbleback

The 2940 is the wartime Bubbleback: the steel, center-seconds, export-friendly expression of the earlier 3131 formula. Its broad dial range reflects the few markets Rolex still had open in the 1940s.

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

Phillips Geneva 2015 lot, rose-numeral dial

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 Bubbleback range, the 2940 sits beside the sub-seconds 2764, the more mixed-metal 3065, and the engine-turned 3372. Steel examples are the standard configuration. 14K gold-top over steel sits above them, and solid 9K gold is the scarcest material. 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 were an unusual export window for Rolex, and the 2940's dial variety reflects that. The reference was sold across different surviving markets, and Rolex was willing to tailor the dial mix to those channels more than on many later references.

The two-piece case

1946 example, profile shows Bubbleback caseback bulge

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

Hooded-lug 2940s should be treated with suspicion. Hooded-lug Bubblebacks are real Rolex watches, but that case form belongs to the 3065, not the 2940. Collector consensus is that most hooded-lug 2940s are modified cases made to imitate the rarer 3065. Caseback stamping and lug geometry are the key checks.

When a 2940 appears for sale with hooded lugs, the presumption is modification. The burden is on the seller to show 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 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 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

Applied rose numerals + sub-seconds register

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-finish dials are scarcer still. The Heritage Auctions "Two Tone Salmon Dial" example, a c.1942 2940, is the best-documented salmon dial in the public auction record, and 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 styles turn up on the surviving 2940s: Mercedes, sword, pencil, and dauphine. That spread matters because the reference was sold into several different market moods at once.

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 clear retailer-specific branch: the Zell Bros "Turtle Perpetual Timer." It is still a standard 2940 underneath, but the name and dial signature are enough to put it in its own small collector lane.

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 from the 2020s puts the 2940 in a modest but real collector band: standard steel lower, unusual dials and precious-metal cases higher. The watch matters more for variation and originality than for headline prices.

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 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

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 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.

Any 2940 offered with hooded lugs should be treated as an aftermarket modification unless the seller can produce clear between-lug 2940 stamping along with professional authentication from a recognized vintage Rolex specialist. The reference's authentic configuration is 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 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.

Sources

• The Vintage Rolex Field Manual — Colin A. White, 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