Audemars Piguet Royal Oak Perpetual Calendar 25654 Explained

In 1978 the Swiss watch industry was in the middle of the quartz crisis. Cheap, accurate battery watches were taking over, and plenty of established brands were cutting back on mechanical watchmaking. Audemars Piguet chose that moment to release a demanding mechanical complication: an ultra-thin, self-winding perpetual calendar.

Six years later, it put that movement inside the Royal Oak. The result took a steel sports watch, a category the Royal Oak is widely credited with defining, and gave it one of the most respected complications in watchmaking. The reference 25654 is one of the watches that carried that idea through the late 1980s and 1990s.

What is a perpetual calendar watch?

A perpetual calendar shows the correct date automatically, allowing for months of different lengths and for leap years. A simple date watch needs correcting at the end of every 30-day month and in February. A perpetual calendar does not, as long as it keeps running.

It does this with a mechanical "program," usually built around a wheel that makes one rotation every four years, so the watch knows which February has 29 days.

There is one known exception. Under the Gregorian calendar, years divisible by 100 are not leap years unless they are also divisible by 400. The year 2000 was a leap year. The year 2100 will not be. A standard mechanical perpetual calendar will therefore need one manual correction after 28 February 2100.

How did Audemars Piguet build its perpetual calendar movement?

The key was thinness. Audemars Piguet unveiled its ref. 5548 perpetual calendar in 1978 with calibre 2120/2800. Monochrome Watches, in its detailed history of the model, describes it as the world's thinnest self-winding perpetual calendar movement at the time, and credits its development to three Audemars Piguet watchmakers: Michel Rochat, Wilfred Berney and Jean-Daniel Golay.

The movement has two parts:

Calibre 2120, the base. An ultra-thin automatic movement only 2.45mm thick, derived from Jaeger-LeCoultre calibre 920. The same base family was used by Patek Philippe as calibre 28-255 and by Vacheron Constantin as calibre 1120. Its rotor runs on a rail around the edge of the movement, supported by small ruby rollers, rather than sitting on top of it. That is a large part of how it stays so slim.
The 2800 module. A perpetual calendar mechanism about 1.5mm thick, produced by the specialist Dubois Dépraz and mounted on the dial side.

Together they measure roughly 3.95mm. For a self-winding perpetual calendar, that is remarkably thin, and it is what made the Royal Oak version possible.

When was the first Royal Oak Perpetual Calendar released?

The first Royal Oak Perpetual Calendar was introduced at the Basel fair in April 1984. It was first numbered 5554 and later 25554, and most examples were made in yellow gold.

It used the same 39mm case diameter as the original Royal Oak "Jumbo" ref. 5402 designed by Gérald Genta in 1972. According to figures published by Monochrome Watches, it measured 7.5mm thick, only 0.4mm thicker than the time-and-date Jumbo. About 279 examples of the 25554 were produced across all metals.

How is the 25654 different from the 25554?

The 25654, introduced in 1987, looks almost identical to the 25554 but has a slightly thicker case. It grew from 7.5mm to about 8.3mm to accommodate a larger metal casing ring and a more robust gasket. Versions with a sapphire caseback measure closer to 8.8mm.

The movement stayed the same: calibre 2120/2800.

According to the same Monochrome history, 851 examples of the 25654 were produced over roughly twelve years:

Yellow gold (BA): 430
Steel (ST): 315
Two-tone (SA): 68
Platinum (PT): 38

Yellow gold, the version featured below, was the most produced of the four. Those numbers come from a single published source, so we present them as reported rather than independently confirmed.

Does the Royal Oak 25654 have a leap year indicator?

No. The first-generation Royal Oak perpetual calendars, including the 25554 and 25654, have no leap year indicator. The mechanism still tracks leap years internally. It simply does not display where you are in the four-year cycle. Audemars Piguet left the display out to keep the movement as thin as possible.

A leap year indicator arrived with calibre 2120/2801, first seen in the Royal Oak in the 1995 anniversary reference 25810, where it appears as a small hand in the month subdial. For collectors, this is one of the easiest ways to tell a first-generation Royal Oak perpetual calendar from a later one.

How do you set a Royal Oak 25654?

The calendar is adjusted through small recessed correctors set into the side of the case, operated with a stylus rather than a fingertip. To make space for them, Audemars Piguet made the hexagonal bezel screws slightly smaller and turned two of them into decorative screws.

From our experience handling these watches, two practical points apply. First, correctors on vintage perpetual calendars are delicate and should be used with the proper tool. Second, as with most perpetual calendars, it is good practice to avoid making corrections in the late evening and early morning hours when the calendar is changing over. If in doubt, ask a qualified watchmaker.

How did the Royal Oak Perpetual Calendar evolve after the 25654?

The perpetual calendar became one of the longest-running complications in the Royal Oak family. A few milestones are worth knowing:

Ref. 25686 (1989 to 1997): made the display caseback standard and introduced special dials to the line, including Tuscany blue and mother-of-pearl.
Ref. 25810 (1995): the 120th anniversary edition in rose gold, limited to 120 pieces, which brought back the leap year indicator.
Refs. 25820 and 25829: later 39mm references with the leap year display, the 25829 being openworked.
Ref. 26574 (2015): a 41mm case and the new calibre 5134, with week and leap year indication.
RD#2 and ref. 26586 (2018 to 2019): the Royal Oak Perpetual Calendar Ultra-Thin, just 6.3mm thick, with calibre 5133 built on the 2120 architecture.
Ref. 26674 (2025): calibre 7138, which sets every calendar function through the crown and does away with case correctors.

In other words, the thin 2120 base that made the 1984 watch possible was still the foundation of an ultra-thin Royal Oak perpetual calendar 35 years later.

Is the Royal Oak 25654 collectible?

In our experience, interest in early Royal Oak complications has grown steadily, and in our view the first-generation perpetual calendars are among the most historically important of them. They represent Audemars Piguet's decision to put serious watchmaking into a sports watch at a time when the industry was retreating from mechanical complications.

When we assess one, we focus on:

Dial condition, including the printing and the moon phase disc.
Correct function of the calendar, checked across month changes.
Service history from a watchmaker experienced with calibre 2120/2800.
Case and bracelet condition, since integrated gold bracelets can show stretch and polishing.

For more on how different Royal Oak references have performed in the market, see our Royal Oak investment guide.

The Royal Oak Perpetual Calendar 25654BA at Investment Watches

We currently have an Audemars Piguet Royal Oak Perpetual Calendar ref. 25654BA from the 1990s, in 18k yellow gold with a white dial and the integrated yellow gold bracelet. It displays day, date, month and moon phase, driven by the self-winding calibre 2120/2800.

If you want to see how far the idea has travelled since, we also have the modern Royal Oak Perpetual Calendar Ultra-Thin ref. 26586IP in titanium and platinum. Seen side by side at our Austin showroom, the two show how far the idea has travelled in four decades.

Quick facts: Audemars Piguet Royal Oak Perpetual Calendar 25654

Introduced: 1987 (succeeding ref. 25554, introduced 1984)
Case: 39mm, approx. 8.3mm thick
Movement: calibre 2120/2800, self-winding, approx. 3.95mm thick
Base calibre: 2120, derived from Jaeger-LeCoultre calibre 920
Functions: hours, minutes, day, date, month, moon phase, perpetual calendar
Leap year indicator: no (first-generation movement)
Reported production: 851 pieces, including 430 in yellow gold