The Audemars Piguet Royal Oak perpetual calendar has been in continuous production since 1984, outlasting most of its integrated-bracelet rivals through successive movement generations. Reference 26685XT.OO.1320XT.01, unveiled in February 2026, is a substantial revision of the line. The dial is gone entirely, the movement is a new generation, and every calendar function is now corrected via the crown alone — no pushers, no stylus, no separate tools. Priced at approximately £158,000 (around $200,000) excluding VAT, it is the first openworked Royal Oak perpetual calendar, introducing a crown-only system that simplifies the use of a mechanism of this complexity.
Engineering Legacy
Audemars Piguet has carried the perpetual calendar through the Royal Oak across multiple generations, refining each calibre until the complication became as integral to the line as the octagonal bezel. The outgoing Calibre 5135 completed its tenure with the 150th Anniversary Openworked edition in 2025. What arrives in its place is a new movement architecture, a new calibre, and no dial.
Calibre 7139 is the openworked version of Calibre 7138, itself derived from the ultra-thin automatic Calibre 7121 base, with all perpetual calendar functions drawn into a single layer. At 4.1mm thick, it is thinner than many dress watch movements with far less complexity. It runs at 28,800 vibrations per hour with a 55-hour power reserve, and the finished case stands at 9.5mm tall across 41mm.
With no dial to organise the display, legibility has to be resolved by the movement itself. The answer is a layered arrangement in which the gear train, calendar mechanism and display indications share the same visual plane. Transparent subdials with lightly smoked outer rings sit above the movement: day at nine o’clock, date at twelve, month and leap year at three, moon phase with a black aventurine disc at six. A central hand covers the week indication around the dial edge. The smoked rings draw the indications forward without obscuring the view beneath, keeping the display legible without simplifying what lies behind it.
The visual continuity with the outgoing 5135 was deliberate. At arm’s length the two movements read as near-identical, and AP made no attempt to signal the generational shift through aesthetics. The architecture beneath is entirely new; the appearance carries forward what the previous reference established.
The case pairs titanium with Bulk Metallic Glass, the latter used for the bezel, caseback and bracelet studs. Satin-brushed titanium sits against mirror-polished Bulk Metallic Glass, producing a two-tone reading without conventional precious metals. Bulk Metallic Glass is significantly harder and more scratch-resistant than gold or platinum, which makes it as practical a choice for high-wear surfaces as it is an aesthetic one.
The midnight changeover, when multiple indicators advance simultaneously in a controlled sequence, is visible rather than concealed. It is one of those details that photographs consistently fail to convey.
The Crown-Only Correction System
AP’s patented crown-only adjustment replaces the traditional corrector pushers found on perpetual calendars for decades. Every calendar function — day, date, month, leap year, moon phase — is set via the crown, without tools and without risk of advancing the calendar out of sequence. On a complication that tracks four indications simultaneously, removing that friction changes how the watch is used day to day, not simply how it is described.
Market Insights
Specialist press reception has been strong, with Calibre 7139 regarded as one of the most capable movements Audemars Piguet has produced in this segment to date. The combination of a new architecture, improved usability, and aesthetic continuity with the previous generation has been well received. The outgoing openworked perpetual calendar continues to hold well on the secondary market, which has done little to dampen confidence in the new reference.
Reference 26685XT is boutique-exclusive, with production highly limited. At £158,000 (around $200,000) excluding VAT, it sits above standard closed-dial Royal Oak perpetual calendars and ahead of most competing integrated-bracelet references at comparable specification.
Secondary market behaviour for openworked Royal Oak perpetual calendars is more selective than for standard Royal Oak steel references. The buyer base is smaller but engaged, and well-maintained examples with clean provenance hold their value. Titanium and Bulk Metallic Glass specifications are viewed favourably by those focused on materials, and boutique-only distribution keeps supply tight.
Servicing Calibre 7139 requires specialist intervention and costs accordingly. Liquidity is lower than for pieces distributed through broader dealer networks, and this segment moves slowly relative to more accessible Royal Oak references. The same exclusivity that supports long-term value makes near-term liquidity limited.
The Long View
Reference 26685XT extends the Royal Oak into high-complication territory with a movement that earns its exposure and a correction system that resolves the principal practical limitation of perpetual calendar ownership. The visual continuity with the outgoing 5135 is preserved, the new architecture is more capable, and the result is a watch that performs as well as it looks. Whether on the wrist or under scrutiny, it holds up.
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