Audemars Piguet

1992 Audemars Piguet Royal Oak Quantième Perpetual Calendar 18K YG (Ref. 25636BA) Openwork "Small Font" Dial W/ Box, Winder, AP COA, AP Extract, AP Service Papers, & Accessories

$ 275,000

First unveiled by Audemars Piguet in 1972 the Royal Oak ref. 5402, designed by Gerald Genta, was the most expensive steel watch ever made. The early 1970s was a time of great change within the watch industry. Audemars Piguet was shaking the standards by introducing a luxury watch in steel that was oversized and pushed the boundaries of the current design trends of the era. This risk had obviously paid off as the Royal Oak is the perfect balance between utilitarian function and timeless design. The case and bracelet are excellently finished, with angular, beveled, and polished edges. The polished screws, bezel, and case edge fantastically contrast with the brushed surface of the case and bracelet to make for one of the most intriguing watches to come out of the era.

Considering the climate of wristwatches in the late 1970s, at the height of the quartz crisis, the concept of designing and manufacturing a mechanically innovative watch was all but lost for most watch brands. Amidst this turmoil, Audemars Piguet seized an opportunity to create, in secret, one of the greatest achievements in horological history. 

Enter the Caliber 2120/2800 — an automatic winding, ultra-thin, perpetual calendar movement, measuring only a mere 3.95mm in height. This movement was based on the ultra-thin caliber 2120 created in 1967 and utilized in several iconic models such as the Royal Oak, Nautilus, and the 222, but was heavily modified to incorporate the perpetual calendar complication. This caliber was initially introduced in 1978 with the model 5548, the original Quantième Perpetual model, and was designed by the protege of Gerald Genta, Jaqulin Dimmer. The Quantième Perpetual quickly evolved through the 80s and 90s, however, each model was produced in very limited quantities, with sometimes less than 100 pieces of a specific metal in a reference. It’s known that 7219 cal. 2120/2800 movements were created over the 15-year production period of the movement.  

While the cal. 2120/2800 was in full production from 1978, it wasn't until 1984 that we would see the first Royal Oak Quantième Perpetual released, however, Audemars Piguet didn't stop there. In further response to the quartz crisis, in 1986 Audemars Piguet released the first Royal Oak Quantième Perpetual in an openwork design, also known as the ref. 25636. "Openwork" is the design art of showcasing the movement through the dial and case back of the watch, revealing the intrinsic value of the wristwatch. However, this was not just simply done, as it took the Audemars Piguet Openwork workshop about 200 hours to fully finish the intricate detailing of each movement. As the global enthusiast's perception shifted from the economic advantages of quartz watches back to the appreciation for mechanical excellence, openwork wristwatches became the forefront of collectibility.

Due to the challenges and time commitment required to openwork a movement as complex as the cal. 2120/2800, only 313 models were produced in the 25636 reference over the course of its 10-year production period, the most desirable of which retain the "small font" Audemars Piguet logo.

Stock # APROQP25636BA
Brand Audemars Piguet
Style Royal Oak Quantième Perpetual Calendar
Model 25636BA
Serial C94XXX / No. 14X
Size Men's
Material 18K Yellow Gold
Dial Openwork "Small Font"
Millimeters 39
Bracelet Audemars Piguet 18K YG Integrated Bracelet



The impressive, angular, and iconic 18K yellow gold case is exceptionally well-preserved exhibiting minimal signs of previous use or polishing while maintaining extremely crisp finishing, angles, and geometry throughout. The case also features a tasteful and attractive rosy patina, a sign that any minor polishing the case may have seen previously was done some time ago. The sapphire crystal is free of blemishes or signs of use. The sapphire display case back is also clean and free of wear, showcasing the exceptionally finished cal. 2120/2800 movement. The 18K yellow gold integrated bracelet exhibits minimal signs of gentle use with almost no stretch present. The bracelet is currently sized to fit a 6 1/2-inch wrist and comes with 3 additional links.


The original "small font" openwork sapphire dial is flawless and beautifully displays the finished top portion of the cal. 2120/2800 movement. The moon phase exhibits a subtle sliver of aging from oxidation at one edge, however, it is virtually invisible to the naked eye. The hands all remain original to the watch and are in perfect condition.


The watch comes with its original outer box and large watch winder, an Audemars Piguet Certificate of Authenticity issued in 2021, an Audemars Piguet Extract From The Archives issued in 2021, Audemars Piguet service papers from 2021, the Quantième Perpetual instruction booklet, and the original setting pusher. The watch is keeping time and functioning perfectly.

More to Explore