Royal Oak Perpetual Calendar Openworked Stainless Steel

In Context

At 39 mm it sits just under the modern norm — the band that suits the widest spread of wrists. At 9.3 mm thick it is about average for a modern wristwatch. The case back is open, so the movement is visible without taking the watch apart, and the sapphire crystal will resist everything short of deliberate abuse. Rated to 20 m, it is protected against rain and splashes and nothing beyond that.

The movement winds itself from the motion of your wrist. 40 hours of reserve carries it overnight, but not through a weekend in a drawer. At 21,600 vph the seconds hand advances 6 times a second, the slower and more audible rate of an older design.

25829ST.OO.0944ST.01 stands on its own in this catalogue — no other reference here shares its base number. It pairs a see-through dial with a stainless steel case. Introduced in 1983. Beyond the time it carries a perpetual calendar.

The 2120/2802 is the ultra-thin perpetual calendar Audemars Piguet built from 1983 on the Jaeger-LeCoultre 920 base. It is the 2120 automatic with a perpetual calendar and moon phase module. It powers 18 watches in this library. The [2121](/calibers/audemars-piguet-ap-2121) is the same base with a date; the 2120 has none, and the 2802 module on top carries the day, date, month, leap year and moon phase, with the moon printed on sapphire. The result is 28.4 mm across with 38 jewels, a 40-hour reserve and a beat of 21,600 vph, and it powered the Royal Oak Perpetual Calendar, the first Royal Oak with a complication, from the 25554 of 1984 through the 25820 and 26252 until the [5134](/calibers/audemars-piguet-ap-5134) replaced it in 2015. The bridges are bevelled, brushed and engraved by hand. The glossary defines the [perpetual calendar](/glossary/perpetual-calendar). In the library it powers 14 [Royal Oak](/brands/audemars-piguet/royal-oak) Perpetual Calendar references at 39 mm and 4 [Jules Audemars](/brands/audemars-piguet/jules-audemars) at 41 mm. 2 are limited editions.

17 other watches in the library run the Audemars Piguet AP 2120 / 2802.

Audemars Piguet

Jules Audemars 26000 Perpetual Calendar Platinum 30th Anniversary

26000PT.OO.D028CR.01 · 41 mm

Audemars Piguet

Royal Oak Perpetual Calendar Pink Gold / Silver / Strap

26252OR.OO.D092CR.02 · 39 mm

Audemars Piguet

Royal Oak Perpetual Calendar Openworked Pink Gold

25829OR.OO.0944OR.01 · 39 mm

Audemars Piguet

Royal Oak Perpetual Calendar Stainless Steel / Silver

25820ST.OO.0944ST.03 · 39 mm