Famed within watchmaking for its avant-garde design, the Royal Oak burst onto the scene in 1972 as the world's first luxury stainless steel sports watch. While created by Audemars Piguet as a means to tackle the growing financial stress they were undergoing due to the Quartz Crisis, the Royal Oak quickly took over AP's other offerings and became their most popular. As a means to bridge the gap between their high complication watchmaking and the Royal Oak's utilitarian functionality, the collection began to grow with complicated variants. Perhaps one of the most iconic is the watch I have here, the Royal Oak Perpetual Calendar Openworked ref. 25636BA.
Designed much like every other Royal Oak that came before it, the Royal Oak Perpetual Calendar ref. 25636BA features a 39mm octagonal case with a plethora of polished and brushed surfaces, sharp bevels, and a beautifully intricate integrated bracelet. Constructed from 18kt yellow gold, the ref. 25636BA depicts the ultra-luxurious aesthetic that AP has become so closely linked with.
Moving on to the star of the show, there are two things about this watch that Audemars Piguet is known for championing: the perpetual calendar and the art of open working.
Beyond its construction, this ref. 25636BA features a stunning sapphire dial that reveals the open-worked perpetual calendar movement that lies beneath; AP's incredible cal. 2120/2800. Showcasing AP's traditional craft of open working, the Royal Oak Perpetual Calendar ref. 25636BA was one of the most intricate and detailed watches from the manufacture and featured not only a complicated movement in a sports watch (which was highly unusual at the time), but also exquisite finishing and engravings throughout.
While today Audemars Piguet is well known for their open working, it was them that first championed it with models such as this 25636BA. This example lies within the first generation of Royal Oak Perpetual Calendars, with the notable absence of a leap year indicator. Even though this perhaps makes the watch less useful, watch collectors prize these references because of their historical importance and rarity.
Limited to just 126 pieces spread over its production period from 1986 to 1996, the Royal Oak Perpetual Calendar ref. 25636BA is a gorgeous watch that is, at its core, a truly mesmerizing piece of horology. With its cal. 2120/2800 displaying some of the most spectacular finishing possible from both its dial side and from behind its exhibition caseback with the inclusion of its ornate 18kt gold winding rotor, the Royal Oak Perpetual Calendar ref. 25636BA remains one of AP's most beautiful and collectible watches, even to this day.