Emmanuel, known as quattro on WatchProSite, delves into a fascinating and often overlooked chapter of Audemars Piguet's history: the 1940s 'world time mnemonic' dials. His meticulous research unearths details about these rare timepieces, which feature a unique, static subdial designed as a memory aid for calculating time differences. Emmanuel's work provides invaluable context for understanding AP's historical approach to world time functionality and its distinctive design language.
In the 1940s,
Audemars Piguet created a few watches with a dial designed like the "
observatory dials", i.e. with
small seconds at 9 o'clock & another,
purely static subdial at 3 o'clock featuring, instead of a precision or observatory mention, a
timezone chart.
The main 24 time zones are symbolised by numerals and the time zones considered "important" (very debatable, of course) include a reference city name.
This simplified World Time system, which requires basic mental arithmetic (the watch doesn't do the math for you!), was designed as a memory aid, facilitating the determination of the time differences between various cities of the world.
These dials were available in different versions as to the "main" or "home" location, always located at 12 o'clock (noon) and sometimes pointed by an arrow. For example, when New-York is located at noon, it is easy to see that Hawaï is -6h and Rome +6h. Or course, daylight saving time isn't taken into account (you'd better know if the different locations use it or not).
These dials with this purely passive world time "complication" have sometimes been called "world time mnemonic dials".
The watches are all powered by calibre 13VZAS.
According to
Monaco Legend Group, only 6 examples are known, but I think
I've identified 13 (if I didn't make any mistake as data is often scarce and unclear)...
Best, Emmanuel
A/ TEARDROP LUGS
1/ Steel - Roma - Probably movement no. 45869 (or 45896)
credit: Hodinkee (1-3) & Antiquorum (the first photo is referenced as 45869, the second one as 45896 but I think it's a mistake as they seem identical)
2/ Steel - Roma - Movement no. 45953
credit: Christie’s
3/ Steel - Roma - Movement no. 45960 
credit: Bukowskis, @wirelug (one before last) & Hodinkee (last)
4/ Steel - Roma - Movement no. 45961
credit: classic driver
5/ Steel - City? - Movement no. 45966
credit: Christie’s
6/ Steel - Roma - Movement no. 46564
credit: Charlotte van Gaver
7/ Yellow gold - Roma - Movement no. 48532
credit: Amsterdam Vintage Watches
8/ Yellow gold - New-York - Movement no. 46605
credit: Monaco Legend Group
B/ CLASSICAL LUGS
1/ Yellow gold - Roma - Movement no. 45967
2/ Yellow gold - New-York - Movement no. 46556 (this example has been sold six times by Antiquorum)
credit: Antiquorum
C/ CLAW LUGS
1/ Steel - Rio Janeiro - Movement no. ?
credit: Hodinkee
2/ Steel - New-York - Movement no. 46557
3/ Yellow gold - New-York - Movement no. 51700 This example, with the timezone chart around the canon pinion and small seconds at 6 o'clock, is unique.
credit: Antiquorum 
