25558BA Audemars Piguet Quantième Perpétuel Openwork

Despite the fact that they’ve almost entirely forgotten about it in favor of things like Spider-Man Royal Oaks, strange permutations of the Code 11.59 that nobody asked for, and stroking John Mayer’s ego, Audemars Piguet saved complicated mechanical watchmaking in 1978 with the reference 5548. This is the 25558, the first openwork (skeletonized) model of that very QP. It was made in 217 examples, 154 of which were this gold. Alongside the VC 43032, the 25558 (and latter 25668) is the ultimate neo-vintage perpetual calendar, although something about the 25558 feels more significant for having created the category and given both VC and Patek the confidence to return to mechanical complication in the wake of the quartz crisis.

What I most love about this movement is that it was developed in secret. AP’s top brass was investing heavily into quartz and it was feared that no budget for mechanical watchmaking would be present in a few years. A team of three senior watchmakers (lead watchmaker Michel Rochat, founder of technical department Daniel Golay, and head of service Wilfred Berney) with immense skill formed their own Skunkworks inside the company. It was deliberately kept secret, for fear of reprimand. Once the lights were turned off at the end of a long day, they would convene. Without AP’s consent and totally unpaid, the three designed late into the evening for years. The result was the world’s thinnest self wound perpetual calendar movement ever, the 3.95mm thin 2120/2800.

The openwork here was created once the 5548 had seen success a little over 5 years later. It’s the victory lap. You’ll find this earliest 25558 features a case with extruded pushers. The latter 25668 only differs slightly in case construction. The engraving, beveling, and angles in the movement will reward hours of louping. The skeleton moonphase is a nice touch too. This calibre was the success that brought AP’s complicated movement making, and most of Switzerland’s, back from the dead (not the Royal Oak). 2120/2800 changed the course of watchmaking history. AP could stand to do more to honor this legacy today, it has just been left to the history books. Its insane development story and market success are proof of the massive difference just a few determined and skilled minds can make.


This example presents in excellent condition, at least from what one can see in images alone. The case is lightly worn and remains very strong lugs, hallmarks, and engravings. Even the tool guide marks for the caseback engravings are visible. It comes as watch only from a well-regarded retailer specializing in neo-vintage.