The ?World Time? system was invented around 1935 by Louis Cottier (1894-1966), famous independent watchmaker in Geneva. This ?World Time? system was used by Patek Philippe and by other major names in the Swiss watch industry, such as Agassiz, Rolex and Vacheron Constantin. Patek Philippe created various series of ?World Timers? from 1937 to the mid-1960?s: Ref. 515 , a rectangular ?galbé? pink gold model made in 1937, with the names of 28 cities on the dial, the time differences between them based on Greenwich Mean Time. It is the earliest known; only three examples are known today. One was sold by Antiquorum, in Geneva, on April 10, 1994, lot 502, for SFr. 550,000 (US$ 388,560). Ref. 542 HU (Ø 28 mm.), started around 1937, bears the names of approximately 30 cities on the revolving bezel. Only 4 examples are known to date, three of which were sold by Antiquorum: - Geneva, October 17, 1993, lot 431, at SFr. 121,000 (US$ 81,700). - Geneva, April 10, 1994, lot 500, at SFr. 231,000 (US$164,200) with unusual bezel and hands. - Geneva, October 15-16, 1994, lot 608, at SFr. 110,000 (US$ 87,300).
Ref. 96 HU Calatrava, with the names of 28 cities on the dial, appears to be a unique example made in 1939.
Ref. 130, of which only one example is known and was made on special order by Patek Philippe in 1939, is an 18K yellow gold mnemonic ?World Time? chronograph wristwatch with square push buttons, register and tachometer. This watch does not have a World Time movement but features a World Time dial with the names of 24 cities. The time difference between the various cities is based on Berlin, which is at noon. This watch was sold by Antiquorum, in Geneva, on April 18-19, 1998, lot 40, for SFr. 355,500 (US$ 235,000), establishing a world record for this type of watch.
Ref. 1415 HU began to be produced around 1939-1940. It has teardrop-shaped lugs, a 31 mm. diameter, and on the revolving bezel the names of approximately 30 to 41 cities. This model was produced: - in yellow gold with silvered dial - in yellow gold with cloisonné enamel dial representing various continents - in pink gold, with silver, champagne or pink dial - in pink gold, with cloisonné enamel dial representing variouscontinents - Antiquorum sold such a watch in Geneva, on November 13-14, 1999, lot 520. It set a World Record for the model, at SFr. 1,345,500 (US$ 868,065). - in platinum with silvered dial, the only one known, was sold by Antiquorum in Geneva, on April 13-14, 2002, lot 608, for SFr. 6,603,500 (US$ 4,026,500), also establishing a world record.
Ref. 1416 HU is similar to Ref. 1415HU and was produced at the same time, with the only difference being that it has straight ?claw? lugs. Three examples are known today. Ref. 1415-1 was created in 1940 for Dr. P. Schmidt. This is a unique World Time chronograph wristwatch, in yellow gold, with square push buttons and the names of 33 cities. It was sold by Antiquorum in Geneva, on October 15-16, 1994, lot 516, attaining what at the time was a World Record, at SFr. 990,000 (US$ 785,714). This watch is illustrated on the front cover and p. 270 of the new edition (1998) of Patek Philippe Wristwatches, by Martin Huber & Alan Banbery.
Ref. 605 HU was produced circa 1940-1960 and is a series of dress watches, with on the revolving bezel the names of approximately 30 to 41 cities. Some examples have a matte silvered or black dial and others have a cloisonné enamel dial.
Ref. 2523 HU and Ref. 2523-1, with two crowns, were produced circa 1953-1965: they bear the names of approximately 40 cities on the revolving bezel. They were made: - in pink gold, with silvered guilloché dial - in pink gold, with translucent enamel dial - in pink gold, with cloisonné enamel dial representing various continents - in yellow gold, with silvered guilloché dial - in yellow gold, with translucent enamel dial - in yellow gold, with cloisonné enamel dial representing various continents - one example is known to date in white gold, with cloisonné enamel dial representing various continents.