Prototype 2523 Patek Philippe World Time

This is the first 2523 made, the prototype. Thanks to records from scholar Brandon Thomas, who acquired original workshop notes from Cottier’s atelier, it’s known that this was marked down as a prototype. Likely made with two different interchangeable center dial styles as test, this example sported this unique guilloché and is also pictured in an archival photo with enamel. The Cottier World Time is one of the most important developments that has been released under Patek Philippe. If there were one watch to document its quick and successive evolution as the market grew fond of it, this 2523 is it.

The movement number, 720’300, is the lowest yet recorded for a 12-400 HU. This was the movement which introduced the second crown at 9 to adjust the inner city ring, a notable evolution. The dial here omits Berlin, which was seen by 1953. Instead of dot indication, this dial features engraved gold sun and moon medallions, which Cottier had already largely stopped making by the late 40s. This is the reason the dual-dial hypothesis in paragraph 1 is supported, as the other example pictured with an enamel dial also sports these same sun and moon engravings.

This is a fascinating exploration into truly special vintage World Times. While the 1415 was first, in production since 1939, the 2523 popularized the complication thanks to ease of use. This prototype laid the ground work which is still alive across multiple collections in 2026. While the dual crowns have been replaced, their idea remains. This early example—with its many disctinct differences and charms—lives amongst the most special multiple time zone watches made. It may not have a cloisonné map as typically favored by collectors, and yet it’s far more special than any of those works. This dichotomy and the unique solid gold guilloché with unique sun and moon medallions make this something outside of most vintage Patek Philippe collecting. It is a watch responsible for developing the complication. And that’s a collecting category of one.