If you want to wear a watch with history, this is a near-unbeatable piece. The original cloisonné enamel dial version from the 1930s is very much in demand, with Europa Star noting the auction price in 2002 for a 1939 platinum Patek Philippe World Time watch as CHF6,603,500. Wristwatches with the cloisonné and world time mechanism from Patek Philippe from the 1940s and 1950s are similarly sought after and fetch high prices on auction.

It is this very watch that is referenced by Patek Philippe with the Ref. 5131, right down to the cloisonné dial. Now, Patek Philippe had already introduced an update of Cotier's world time mechanism with Ref. 5110, where they dispensed with the second crown. A pusher at 10 o'clock took its place, simplifying the action of time setting. One can traverse all 24 time zones on the watch by using the pusher 24 times.

What actually happens is this: a single depression of the push piece advances the hour hand by one step. Simultaneously, both the city and 24-hour discs move back a step. In this watch, the local time always refers to the city that is in line with the hour marker at 12 o'clock. The scale of this marker is divided over 24 hours, making it impossible to confuse night with day.

This is how it works, practically. Assume your home city is London, as in this image. The local time is obviously 10 o'clock, as is the time indicated by the hour marker at 12 o'clock. Now, as you travel forward one time zone, you advance the local time to 11 o'clock by pressing the pusher. London stays at 10 o'clock by moving one step back, along with the aforementioned hour marker.