Ref. 1415 HU (Heure Universelle) and Ref. 1415 HU DE (Decor Email) P P roduction of Ref. 1415 HU started in 1939 with the delivery of the first 6 movements by Louis Cottier. The following 6 movements were delivered in 1941, then 7 movements in 1942, and so on, until 1946. Between 1947 and 1951 Patek Philippe received 72 move-ments, then nothing until the last movement was delivered in 1954, bringing the total to circa 115 pieces. For ten years, dials were silvered, sometime s champagne or pink. In 1948 Ref. 1415 HU DE (Décor Email) appears in the catalogue as an option to the Ref. 1415 HU, with a different world map according to the retailer's location, usually depicting the Americas, Europe, Eurasia or sometimes the world. Three kinds of dial indexes have been used: - 1st series, enameled black indexes (usually indelible) and concentric Roman numerals at 3, 6, 9 and 12, as seen in Patek Philippe?s General Catalogue of 1939. - 2nd series: enameled black indexes (usually indelible) and concentric applied gold Roman numerals at 3, 6, 9 and 12, as seen in the 1943 and 1947 General Catalogues. - 3rd series: applied gold indexes and applied gold concentric Roman numerals at 3, 6, 9 and 12, as seen in 1950 Patek Philippe General Catalogue.. Cloisonné enamel dials usually bear the 3rd series indexes. The cities on the bezel could differ, depending on the watch?s destination; they began with 28 cities in 1939 and contained as many as 42 in the 1950s, usually written in French or English. Estimated case distribution: 32 examples in pink gold; 82 examples in yellow gold; and 1 in platinum. The "World Time" System W W as invented around 1935 by Louis Cottier (1894-1966), a famous independent watchmaker in Geneva. This system is used by Patek Philippe and by other major names in the Swiss watch industry, such as Agassiz, Rolex and Vacheron Constantin. Patek Philippe created different types of "World Times" from 1937 to the mid-1960s, the latest ones were retailed until the mid-1970s: - Ref. 96 HU Calatrava appears to be an unique example made in 1939, it bears the names of 28 cities in the world written on the cen-tral part of the dial. - Ref. 130, the only example known, was made to special order by Patek Philippe in 1939. It 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, with Berlin being placed at noon. This watch was sold by Antiquorum 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. 515, a rectangular "galbé" pink gold model made in 1937, with the names of 28 cities on the dial, the time difference based on Greenwich Mean Time. This is the earliest of the "World Time" pieces; only 3 examples are known today, one of which was sold by Antiquorum Geneva on April 10, 1994, lot 502, for SFr. 550,000 (US$ 388,560). - Ref. 542 HU Ø 28 mm., produced in 1937 and 1938, bore the names of approximately 30 cities on the revolving bezel. Only 4 exam-ples are known to date, 3 of which were sold by Antiquorum Geneva: October 17, 1993, lot 431, for SFr. 121,000 (US$ 81,700); April 10, 1994, lot 500, for SFr. 231,000 (US$164,200) with unusual bezel and hands; October 15-16, 1994, lot 608, for SFr. 110,000 (US$ 87,300). - Ref. 605 HU was produced circa 1942-1964 and is a series of dress watches, with the names of approximately 30 to 41 cities on the revolving bezel. It usually comes with matte silvered dial, some have a cloisonné enamel dial, fewer have a black dial. - Ref. 1415 HU was produced from 1939 to 1954. It has drop-shaped lugs, 31 mm in diameter and, on the revolving bezel, the names of 28 to 42 cities . This model was produced in yellow or pink gold with silvered dial, rarely with champagne or pink dial, and some-times, after 1948, with cloisonné enamel dial representing various continents. Antiquorum Geneva sold one on November 13-14, 1999, lot 520, which set a world record at SFr. 1,345,500 (US$ 868,065) for this model. - Ref. 1415-1 was created in 1940, especially 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 Geneva, on October 15-16, 1994, lot 516, at the time setting a world record at SFr. 990,000 (US$ 785,714). This watch is illustrated on the cover and p. 270 of Patek Philippe Wristwatches", by Martin Huber & Alan Banbery, 1998 edition. - Ref. 1416 HU, similar to Ref. 1415 HU, was produced from 1939 to circa1947, the only difference being its straight "claw" lugs. Three examples are known today. - Ref. 2523 HU, with two crowns, produced from 1953 to 1965, bears the names of approximately 40 cities on the revolving bezel. They were made in yellow or pink gold, with a silvered or pink dial, usually guilloché. A pink gold example is known with a matte black dial. It also existed with a translucent enamel dial, usually blue, or a cloisonné enamel dial representing various continents; only one exam-ple is known to date in white gold with a cloisonné enamel dial representing various continents. - Ref. 2523-1, with slightly smaller lugs than Ref. 2523, produced circa 1957 to 1974, was in yellow or pink gold, with silvered or pink dial, matte or guilloché. So far, this particular reference has never been seen with a cloisonné dial. Ref. 1415 watches are illustrated in "Collecting Patek Philippe Watches", by Osvaldo Patrizzi, Guido Mondani Editore, Genova, 2004, p. 202 to 203 (vol.1) and p. 91 to 94 (vol.2). Patek Philippe "World Time" wristwatches are published in "Patek Philippe Wristwatches" by Martin Huber & Alan Banbery, 1998, pp. 240 to 247. Information and research: T.E.C.H. data (c).