Patek Philippe "World Time" wristwatches, with two crowns, have the Ref. 2523 HU (heures universelles) and production began in 1953. The two crowns have separate functions: the crown at 3 o'clock adjusts the hands and the 24-hour ring; while the crown at 9 o'clock operates the disc with the names of 41 cities in the world. Production of the first series of the Ref. 2523 began in 1953 with 7 examples in pink gold, of which 4 were with cloisonne enamel dial. Production was continued, with the Ref. 2523/1, in small quantities until the mid-1960's, and these models were only made in yellow gold, white gold and pink gold, though the exact numbers for each are difficult to establish. This series features different types of dials: ? matt silvered. ? guilloche (or engine-turned), either on silver dial plate or on gold dial plate. ? enamelled, such as blue enamel. ? polychrome cloisonne enamel representing a map of North America, or South America, or Eurasia. Generally all Ref. 2523 wristwatches have the same type of hands and it is very rare, even unique, to fmd a model featuring skeleton luminescent hands, as is the case for lot 497 of this sale, which is a Patek Philippe `World Time" wristwatch, Ref. 2523/1, made in 1965, in yellow gold with guilloche dial, on silver dial plate, and with skeleton luminescent hands. The "World Time" system was invented around 1935 by Louis Cottier, famous independent watchmaker in Geneva. This "World Time" system was used by Patek Philippe and also by other major names in the Swiss watch industry, such as Agassiz, Vacheron Constantin and Rolex. Patek Philippe created various series of "World Timers" and the earliest known is a probably unique rectangular "galbe" pink gold model, Ref. 515, made in 1937 which was sold by Antiquorum, Geneva, April 10, 1994, lot 502, for SFr. 550'000 (US$ 388,560). From 1937 until about 1940, Patek Philippe used the `World Time" movement in various types of cases: Ref. 96 "Calatrava", which appears to be an unique example; Ref. 542, which was probably made in 4 examples, and among them three were sold by Antiquorum: - Geneva October 17, 1993, lot 431, at SFr. 121'000 (US$ 81,700) - Geneva, October 15-16, 1994, lot 608, at SFr. 110'000 (US$ 87,300) - Geneva, April 10, 1994, lot 500, at SFr. 231'000 (US$ 164,200), the latter with unusual bezel and hands. Around 1939-1940 began the production of the series Ref. 1415, together with a probably unique Ref. 1416. In 1940, Patek Philippe created, specially for Dr P. Schmidt, a unique "World Time" chronograph wristwatch, in yellow gold, with square push buttons and the names of 33 cities of the world, which was auctioned by Antiquorum, Geneva, October 15-16, 1994, lot 516, setting a World Record at SFr. 990'000 (US$ 785,714). This watch is illustrated on the front cover of the new edition (1998) of Patch Philippe Geneve, Wristwatches, by Martin Huber and Alan Banbery From 1940 onwar ds, Patek Philippe produced "World Timers" in three main series which include dress watches ( Ref. 605, circa 1940- 1960's), some with a matt silvered dial and others with a cloisonne enamel dial; and, wristwatches, with one crown (Ref. 1415, circa 1939-1950's) and two crowns (Ref. 2523, circa 1953-1965), some with a matt silvered or gilt vial, some with a guilloche dial, some with an enamel dial and some with a cloisonne enamel dial. The overall world record for a Patek Philippe "World Time" wristwatch, Ref. 2523, with two crowns, was set by Antiquorum ill.. April 1998 (see below). The best auction results realized, since 1989, for a Patek Philippe "World Time" wristwatch, Ref. 2523, or Ref. 2523/1, with two crowns, are listed below together with the differences in terms of dial and colour of gold: ? Antiquorum, Geneva, April 18-19, 1998, Lot 204: PINK gold wristwatch, Ref. 2523, made in 1953, with cloisonne enamel dial representing North America, sold for SFr. 1'433'500 ( US$ 950,000/UI E 561,276) - Overall WORLD RECORD; and a WORLD RECORD for a Ref. 2523 in PINK gold with cloisonne enamel dial. ? Antiquorum, Geneva, October 21-22, 1995, Lot 918: WHITE gold wristwatch, Ref. 2523, cir ca 1957, with cloisonne enamel dial representing North America, sold for SFr. 902'000 (US$ 791,228) - WORLD RECORD ? Christie's, London, March 17, 1998, Lot 213: YELLOW gold wristwatch, Ref. 2523/1, made in 1954, with guilloche dial, on silver dial plate, sold for UK£ 293,000 (SFr. 721'512/US$ 492,240) - WORLD RECORD The PREVIOUS World Record, for this exact type of wristwatch, was set by Antiquorum, Geneva, in October 15-16, 1994, lot 609, at SFr. 308'000 (US$ 244,450). ? Sotheby's, New York, March 9, 1998, lot 493: YELLOW gold wristwatch, Ref. 2523, circa 1953, with guilloche dial, on gold dial plate, sold for US$ 420,000 (SFr. 625'000) - WORLD RECORD ? Antiquormn, Geneva, April 12-13, 1997, lot 600: YELLOW gold wristwatch, Ref. 2523, made in 1953, with blue translucent enamel dial, sold for SFr. 652'500 (US$ 456,300) - WORLD RECORD ? Antiquorum, Geneva, April 9, 1989, "The Art of Patch Philippe", lot 294: YELLOW gold wristwatch, Ref. 2523, circa 1955, with cloisonne enamel dial representing North America, sold for SFr. 396'000 (US$ 240,000) - WORLD RECORD This result was exceptional for the time but should such a watch come to auction nowadays it would more than likely realize over twice that figure.