Rolex 2240 Bubbleback

The 2240 is a self-winding Oyster Perpetual in a 32mm stainless steel tonneau case, and it is the one reference in its cohort that still has a claim to the Bubbleback name once the evidence is checked. The collector list that put the 2240 into circulation also lists the 1873 and the 2765, and both of those turn out to be hand-wound flat-back Oysters wearing the Bubbleback's case but none of its mechanics. The 2240 is different: both Antiquorum examples are described as centre-second and self-winding, on a 9¾-ligne movement, which is the size Rolex used for its automatic Perpetual calibers and not the 10 to 10½ lignes of the manual flatbacks.

The thing the nickname actually refers to went undocumented for thirty years. Neither 1995 catalogue says whether the caseback is domed, and neither of their photographs shows it. A third example surfaced in March 2026 at a general auctioneer in Nottingham, catalogued as a ref. 2240 and photographed from the back, and that back is domed. It is the first image of a 2240 caseback in the public record. It is also one non-specialist house's attribution on a watch whose dial reads only Rolex Oyster, without the Perpetual signature both Antiquorum examples carry, which strengthens the Bubbleback reading without closing it.

It is still, by some distance, the least seen watch in the group. Three lots exist in the public record: two Antiquorum sales in 1995 and one English provincial sale in 2026.

Core facts

detail	value
reference	2240
family	Bubbleback (Oyster Perpetual)
production	1930s or 1940s; catalogues disagree, no firm years documented
case diameter	32mm
case shape	tonneau
case	polished and satined, screwed back and crown, waterproof
caseback profile	domed, coin-edged screw-down back on the 2026 Arthur Johnson example; neither 1995 catalogue states it and neither 1995 photograph shows it
bezel	smooth, polished
crystal	acrylic
crown	screw-down
winding	self-winding
seconds	centre seconds
movement	9¾ lignes, rhodium-plated, 19 jewels, lever escapement, monometallic balance, self-compensating Breguet balance-spring. No caliber number published
case materials	stainless steel (all three documented examples)
dials documented	mat silver with applied gold indexes; mat silver with painted Arabic numerals, bâton radium hands on both; silvered sector dial with applied Roman numerals and gilt leaf hands
dial designations	"Oyster Perpetual, Superlative Chronometer, Officially Certified"; "Oyster Perpetual Chronomètre"; "Rolex Oyster"

Where it sits in the line

Two details separate the 2240 from the Bubblebacks that get written about. It has centre seconds rather than the sub-seconds register at six o'clock that the earliest Perpetuals carried, and it has nineteen jewels against the seventeen of the Cal. 520 and Cal. 620 families that powered the reference's better-known neighbours.

That combination places it later in the Bubbleback story than the 1933-era three-piece watches and squarely among the mature automatics — the generation running on the two-piece Oyster case that arrived in 1936 with the 3131 and 3132. Centre-seconds Perpetuals of this era are well attested elsewhere in the family; catalogued 2940 examples carry "luminous filled sword hands, center seconds", so the layout is not anomalous for the period. It is simply not the layout most people picture when they hear Bubbleback.

Where exactly the 2240 falls inside that window is the problem, and the two surviving lots make it worse rather than better. Antiquorum dated its Geneva example to the 1940s and its Hong Kong example to the 1930s, two months apart, in the same year. Both readings stand in the record. The 1936 start year that circulates for the reference comes from the same unverified collector list that mis-assigns its neighbours, and has no independent support behind it.

Production outline

The public record for the 2240 consists of three lots. Two are Antiquorum sales from 1995: Geneva at the Hôtel des Bergues on 22 April, lot 304, and Hong Kong at the Hotel Furama Kempinski on 14 June, lot 29. A full sweep of the house's archive, which reaches back to 1974, returns nothing else, and no lot surfaced at Phillips, Sotheby's, Christie's, Bonhams or Heritage. The third is later and a great deal humbler: Arthur Johnson & Sons, a general auctioneer in Nottingham, sold one as lot 7287 in a mixed Saturday sale on 14 March 2026, catalogued in a single line as an Oyster Bubbleback, ref. 2240, with an automatic movement.

No lot page published a case number, so no serial anchor exists and no production window can be constructed from observed examples. No production figures appear in any documented source. All three documented watches are stainless steel; whether Rolex built the 2240 in gold, gold shell or two-tone, as it did across much of the contemporary range, is unknown.

There is a plausible reason the reference is so scarce in the record, offered here as speculation rather than fact. Both Antiquorum sales predate the internet-era auction archives that most collector research now runs on. The 2026 lot shows the other half of the problem: it passed through a provincial general auctioneer, described in one line, indexed nowhere that vintage Rolex collectors habitually look. A reference can stay invisible by selling in the wrong century or in the wrong room.

Movement notes

Nine and three-quarter lignes, rhodium-plated, nineteen jewels, lever escapement, monometallic balance, self-compensating Breguet balance-spring, self-winding, centre seconds. Both Antiquorum catalogues give that specification word for word, independently, on opposite sides of the world and two months apart.

The ligne size is the most useful number in the description, because it is the one that places the watch. Nine and three-quarter lignes is the size of Rolex's automatic Perpetual movements — the lineage running from the Cal. 520 of 1933 through the 620 and its sweep-seconds successors. The manual-wind flat-back Oysters Rolex was building alongside them run larger, at 10 to 10½ lignes; all three documented examples of the neighbouring ref 2765 measure in that range. The 2240's movement therefore sits inside the automatic family on its dimensions alone, which is independent corroboration of the self-winding descriptions rather than a restatement of them.

Neither catalogue names a caliber, and this article does not supply one. The 19-jewel centre-seconds configuration is architecturally distinct from the 17-jewel sub-seconds Cal. 520 and Cal. 620 that powered the earlier Bubblebacks, and it would be easy to reason from that to a specific sweep-seconds caliber. No documented source makes that attribution for the

The ligne size, the jewel count, the escapement, the balance and the seconds layout are

what the record supports.

Dial map

Three dials are documented, one per lot, and the sale photographs confirm all three.

The Geneva example carries a mat silver dial with applied gold indexes and radium-filled bâton hands, reading Oyster Perpetual below the coronet and carrying its chronometer designation above six o'clock. The Hong Kong example is the more obviously pre-war of the two: mat silver again, but with painted Arabic numerals at every hour, an outer minute track with five-minute markers, Chronomètre above six, and the same radium-filled bâton hands.

The Nottingham watch is the outlier, and the way it differs matters more than the way it looks. Its dial is silvered with a faint sector pattern, applied Roman numerals at the even hours and applied batons at the odd ones, a printed outer minute track, gilt leaf hands and a centre seconds hand. The surface is heavily crazed and plainly unrestored. What it does not carry is the word Perpetual: the signature reads Rolex Oyster and nothing else, where both Antiquorum dials name the watch an Oyster Perpetual and give a chronometer designation. Rolex's self-winding watches of this period almost always say so on the dial, so an original Rolex Oyster dial on a watch sold as an automatic 2240 is a genuine discrepancy and is recorded here as one.

Applied indexes against painted Arabics is a real stylistic split and not a cataloguing quirk, and it maps onto the two dating readings the catalogues give: the painted-Arabic Hong Kong watch reads as the earlier of the pair. Three examples is not enough to call that a production sequence, but it is enough to say the reference was built with more than one dial treatment.

One detail on the Geneva dial deserves a flag rather than a conclusion. Its lot title gives the designation as Superlative Chronometer, Officially Certified, wording generally associated with a later period than the 1940s that the same lot assigns the watch. That could point to a later example, a replacement dial, or simply Antiquorum paraphrasing in the title. The chronology of Rolex's shift between the two chronometer designations has not been checked against independent sources here, so nothing is concluded from it.

Case, bezel, crystal, and crown

Stainless steel, tonneau-shaped, 32mm, polished and satin-finished, with screwed back and screw-down crown. Smooth polished bezel and an acrylic crystal, as the era requires. The Hong Kong catalogue adds one word the Geneva one does not: it calls the case massive, Antiquorum's term for a case with real substance to it.

The caseback was the open question for thirty years, and it is the one that matters most. Neither 1995 catalogue states whether it is domed. Both give the case description in full and both stop at "screwed back and crown". The two Antiquorum photographs are front three-quarter views on leather straps, and neither shows the back at all.

The Nottingham sale turned the watch over. Its fifth photograph is a caseback view, and the back is a pronounced dome seated inside a coin-edged screw ring, the profile the nickname describes. The crown stands proud of the case in the same frame, which fits the one condition note the lot carried: the crown would not screw down and wanted attention.

That earlier silence was never as damning as it looked, because the catalogues of the period do not describe caseback doming even when the watch is unambiguously a Bubbleback. Christie's catalogued a ref 2764 as an Oyster Perpetual Bubble Back in the lot title and then described it in body text as a 9¾-ligne, 19-jewel, sweep-seconds movement in a two-part 32mm case with a domed crystal and a screw-down back and crown. The only thing domed in that description is the crystal. Strip the title away and it reads exactly like the two Antiquorum 2240 lots. The formula does not discriminate, which means the 2240's description is consistent with a Bubbleback and simply fails to settle the question.

Everything else points the same way. That Christie's 2764 specification — 9¾ lignes, nineteen jewels, sweep seconds, 32mm, screw-down back — is the 2240's specification line for line. And the flat-backed automatics that make self-winding an insufficient test are a later development in the 6000-series references, arriving once Rolex had slimmed the calibers enough to drop the bulge. A 32mm self-winding tonneau Oyster running a 9¾-ligne movement in the late 1930s or 1940s sits before that change.

So the reasonable reading is that the 2240 is a Bubbleback, and there is now a photograph of a domed back on a watch catalogued as one. The reading is better supported than it was and still short of settled. That photograph comes from a general auctioneer running a mixed Saturday sale, not from a watch specialist; no case number was published to anchor the attribution independently; and the same watch wears a Rolex Oyster dial without the Perpetual signature both Antiquorum examples carry. A specialist cataloguing of that watch, or a case number, would close the question.

Bracelets, end links, and clasps

Nothing is documented. Neither lot was sold on a Rolex bracelet, and no period fitment for the reference appears anywhere in the surfaced record.

Auction record

Venue	Date	Lot	Dated by catalogue	Dial	Estimate	Result
Antiquorum, Geneva (Hôtel des Bergues)	1995-04-22	304	1940s	Mat silver, applied gold indexes, bâton radium hands	CHF 2,600–2,800 (USD 2,200–2,400)	Not published
Antiquorum, Hong Kong (Hotel Furama Kempinski)	1995-06-14	29	1930s	Mat silver, painted Arabic numerals, bâton radium hands	HKD 15,000–18,000 (USD 2,000–2,200)	Not published
Arthur Johnson & Sons, Nottingham (The Saturday Auctions)	2026-03-14	7287	Not dated	Silvered sector, applied Roman numerals, gilt leaf hands	Not published	GBP 680 hammer

Neither Antiquorum lot page carries a realised price, so for thirty years the reference had no auction result on record at all. What it had instead was two estimates set within about ten percent of each other by the same house in the same year, on two continents, roughly USD 2,000–2,400 either way. The single realised figure the reference now has is the GBP 680 hammer at Nottingham in 2026, which prices a worn, unrestored watch with a crown fault in a sale that was not looking for a Rolex collector. Three data points spread over thirty-one years, two of them unrealised estimates, do not describe a market, and no attempt to read one is made here.

What the three lots do establish is narrower and more useful: that the reference exists, that the two specialist-catalogued examples are self-winding on a 9¾-ligne movement with centre seconds and nineteen jewels in a 32mm steel case, that it appeared with at least three dial treatments, and that a watch catalogued as a 2240 has a domed back.

Related references

Bubbleback 2764 — Cal. 620N "Super Precision"
Bubbleback 2940 — centre-seconds contemporary
Bubbleback 3131 — the 1936 two-piece case transition
Oyster Chronometer 2765 — the manual flat-back that shares the list but not the mechanics
Oyster Royal 1873 — manual flat-back Oyster

Sources