Audemars Piguet made a big splash at SIHH 2018 when it introduced the Royal Oak RD#2 Perpetual Calendar Ultra-Thin, a concept watch that claimed the title of being the world’s thinnest automatic timepiece featuring a perpetual calendar. When that watch was shown to the press during the annual Geneva showcase, there was no word on whether or not it would make it past the developmental stage and into regular production. Earlier this summer, we finally got our answer when Audemars Piguet quietly updated its website to feature an updated take on the concept, the Royal Oak Selfwinding Perpetual Calendar Ultra-Thin.
While the height of the watch (6.3 mm) and the movement (2.89 mm) remain the same as the RD#2, AP made a number of aesthetic updates from the 2018 announcement. Most notably, the characteristic “Grande Tapisserie” dial that defines the Royal Oak’s appearance has been wiped clean for the production run in a bid to cultivate a cleaner and more legible aesthetic. While the dial color — and matching subdials — remains an attractive shade of blue, AP has applied a detailed satin finish to the watch’s face. Optimized readability was key for AP with this release, so the day, date, and month subdials were all enlarged compared to previous RO Perpetual Calendar models, like the Ref. 26574.
Another key change from the prototype version is the material used in the case and bracelet. Where the RD#2 was constructed entirely from 950 platinum, AP has combined titanium and platinum in the finalized version for enhanced wearability. The bracelet and case are made from titanium, while the bezel and bracelet links are built from 950 platinum. Just like with most Royal Oak designs, the case finishing features a blend of polishing and satin brushing. Other noteworthy aesthetic features include the presence of white gold applied hour indexes and the customary Royal Oak hands filled with lume, the symmetrical placement of the night and day indicator at 8 o’clock and the leap year indicator at 4 o’clock, and the presence of an astronomic moon-phase at 12 o’clock, a reference to the first Audemars Piguet perpetual calendar wristwatch released in 1955.
While Bulgari seems intent on claiming as many thinness records as possible within its Octo Finissimo line, Audemars Piguet is no slouch when it comes to the historic production of ultra-thin timepieces. All the way back in 1921, the brand released the world’s thinnest pocketwatch with a movement sized at just 1.32 mm. In 1967, Audemars Piguet released Caliber 2120, which stood as the thinnest automatic movement of its time measuring at 2.45 mm. Finally, in 1978, the brand released what was, at the time, the thinnest automatic perpetual calendar wristwatch with a caliber sized at 3.95 mm, a record now surpassed by the new Royal Oak Selfwinding Perpetual Calendar Ultra-Thin.
So, how exactly did AP beat its former record? Over a five-year period, the brand explored ways to subsidize the watch from a three-story movement — standard for most perpetual calendars — to a single level by combining various functions into single mechanisms. For example, the end-of-the-month cam has been integrated to the date wheel, while the month cam has been combined to the month wheel. The end result of this is the new Caliber 5133 that uses over 250 parts in its construction and offers up to a 40-hour power reserve.
While Caliber 5133 is the result of a strenuous development process, it actually uses the famous Caliber 2120 (the same movement AP used in its 1967 record-breaking release) as a base. What’s interesting about this movement is the presence of a suspended barrel, meaning there is no upper bridge, and the design of the rotor, which places a majority of its weight along the periphery of the caliber where it’s further supported by a beryllium ring and additional jewels. The more standard Royal Oak Perpetual Calendar models use the same base caliber for Caliber 5134, the taller predecessor to this year’s ultra-thin release. While it’s not apparent from the outside (both the standard and ultra-thin RO Perpetual Calendars are sized at 41 mm), AP had to stretch the dimensions of Caliber 5133, which measures 32 mm compared to 29 mm in Caliber 5134, to counteract the shrinkage in height.
A boutique exclusive, the Audemars Piguet Royal Oak Selfwinding Perpetual Calendar is now available for CHF 140,000. The brand says that it will be available in limited quantities, but doesn’t specify a definite number.