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What is the Audemars Piguet BA4266P002?
BA4266P002 is a vintage Audemars Piguet model represented in a 2023 Time+Tide feature by a watch identified as dating to 1985. That dealer-linked example is described as having an 18-karat yellow-gold case, sapphire crystal, and a skeletonised, gilt, hand-engraved display powered by automatic Calibre 2120. The listing gives a 31 mm case diameter, 37 mm lug-to-lug, 18 mm lug width, and 36 jewels. These are details for that documented example, not proof that every watch bearing the reference is in identical condition or configuration. Time+Tide’s feature was published in partnership with the dealer whose listing it discussed.
The octagonal case can call to mind the design language associated with Gérald Genta and the Royal Oak. Time+Tide makes that visual connection, but presents the BA4266P002 as a separate, lesser-known model—not as a Royal Oak. Its appeal is more intimate than the familiar sports-watch silhouette: a small gold case frames a movement whose structure and decoration are part of the display.
Why Calibre 2120 matters
Audemars Piguet’s historical account dates the beginning of the Calibre 2120 project to 1963 and the first delivered examples to 1967. At 2.45 mm high, the movement became the world’s thinnest automatic calibre with a central rotor at the time; AP says it retained that distinction for decades. It was developed from the brand’s Calibre 2003. The date-bearing Calibre 2121 was a later derivative used in the first Royal Oak, but the BA4266P002 example is identified with Calibre 2120, not 2121. See AP’s technical history, “Le Calibre 2120-2121” in AP Chronicles.
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How the rotor works
Rather than relying solely on a central pivot to support the oscillating weight, Calibre 2120 carries its rotor around the movement’s perimeter on ruby rollers running along a circular rail. The arrangement helps make a very thin automatic movement possible. AP also records bidirectional winding and a frequency of 19,800 vibrations per hour. In an openworked example, the rail-and-roller system is not hidden: it becomes part of the visual experience, alongside gilt bridges and a gold rotor.
What skeletonisation involves
Skeletonisation is not simply removing material to make a movement look airy. AP describes cutting away portions of the bridges with a small saw called a bocfil, while retaining the structure needed for the mechanism to function. The resulting components are then decorated by hand. The work demands time and manual dexterity because each opening must reveal more of the movement without compromising its operation.
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AP traces its renewed investment in skeletonisation to the quartz era. The company had practiced the craft in the 1930s through the 1950s, but it had largely disappeared from its workshops. AP revived it to make mechanical watchmaking skill visible, establishing a dedicated workshop where experienced watchmakers could train newer artisans. Time+Tide calls the BA4266P002 a culmination of that revival; that is the feature’s interpretation, rather than an official production designation.
How it relates to the Royal Oak—and how it does not
The connection is historical and visual, not a basis for reclassifying the watch. Calibre 2120 belongs to the movement lineage from which the date-bearing 2121 later emerged, and the BA4266P002’s octagonal case invites comparison with the design vocabulary associated with Genta. But the documented BA4266P002 uses Calibre 2120 and is described as a distinct model. A resemblance or shared movement ancestry does not make it a Royal Oak.
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What is known about its rarity and price?
Time+Tide reported in April 2023 that three examples had reached the market since 2012. That is a dated observation about appearances on the market, not an official count of watches made or a complete census. The same feature gave a $25,000 asking price for its featured example in 2023. That figure is historical listing context, not a current valuation. The cited sources establish no official production total, comprehensive current market count, current price, or present availability.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to research an individual BA4266P002
A reference identifies a model family and shared characteristics; it does not authenticate a particular watch or establish that its components, history, and accessories are original. Audemars Piguet explains that individual movement and case numbers are recorded in production and case registers, distinct from the model reference. Its reference guide identifies “BA” as a yellow-gold material code, but warns against reading every character of an older reference through later conventions. Consult AP’s numbering guidance in AP Chronicles and request documentation tied to the watch’s actual numbers.
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- Match the identity: compare the engraved movement and case numbers with Audemars Piguet documentation. A reference by itself is not a provenance record.
- Verify the movement: confirm the calibre visible in the watch and reconcile it with the documentation. The cited BA4266P002 example is listed with Calibre 2120.
- Inspect condition and originality: assess the gold case for wear and prior polishing, and examine the openworked and engraved components for integrity and legibility.
- Review servicing: ask for records of service and clarify what work was done; the supplied model description alone says nothing about a particular watch’s service history.
- Separate the watch from its accessories: establish whether the strap, buckle, box, and papers are original to the watch or later additions.
- Compare like with like: weigh documented identity, movement condition, case and engraving condition, completeness, and the way the 31 mm example wears. Compare asking prices only across dated examples that are genuinely comparable.
For a small, openworked dress watch, the 31 mm case measurement is only a starting point: the listed 37 mm lug-to-lug dimension and the watch’s actual condition also matter to how it sits on a wrist. The listing’s measurements should be verified against the specific example being considered.
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