Only two examples in yellow gold with blue translucent enamel dial are known to date. The use of the colour blue can be seen as symbolizing the expanse of sky and sea between the 41 cities on the revolving dial. These two watches with consecutive movement numbers, have previously been offered by Antiquorum. The present watch was sold u Hong Kong, on May 30, 1989, lot 252; and, the other (movement No. 722704, case No. 306209), was sold in Geneva, on April 13, 1997, lot 600). PATEK PHILIPPE "WORLD TIME", REF. 2523 AND REF. 2523-1 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 golf, white gold and pink gold, though the exact numbers for each are difficult to establish. The lugs of the 1950's series are more prominent than those of the 1960's series , which are somewhat flattered. 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 translucent enamel. ? polychrome cloisonne enamel representing a map of North America, or South America, or Eurasia. The "World Time" system was invented around 1935 by Louis Cottier (1894- 1966), famous independent watchmaker in Geneva. This "World Tithe" system was used by Patek Philippe and also by other major names in the Swiss watch indust r y, such as Agassiz, Rolex and Vacheron Constantin. Patek Philippe created various series of "World Timers" and the earliest known is a probably unique rectangular "galbe" pink golcl 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. 542, of which only 4 examples are known to elate and 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) with unusual bezel and hands. Ref. 96 "Calatrava", which appears to be an unique example, made in 1939. Around 1939-1940 began the production of the series Ref. 1415 (drop-shaped lugs), together with three examples of the Ref. 1416 (str aight lugs). In 1940, Patel Philippe created, specially for Dc P. Schmidt, a unique "World Time" chronograph (Ref. 1415-1) wristwatch, in yellow gold, with square push buttons and the names of 33 cities of the world, which was auctonecl by Anuquortmz, 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 Patek Philippe Geneve, 1Vrisiwatches, by Martin Huber and Alan Banbery. From 1940 onwards, Patek Philippe produced "World Timers" in three main series which include dress watches (Ref. 605, circa 1940- 1960's), some with a matt silverecl dial and others with a cloisonne enamel dial; and, wristwatches, with one crown (Ref. 1415, circa 1939-1950's), and two crowns (Ref. 2523 and Ref. 2523-1), circa 1953-1965), some with a matt silvered or gilt dial, some with a guilloche dial, some with an enamel dial and some with a cloisonne enamel clial. 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 golcl wristwatch, Ref. 2523, made in 1953, with cloisonne enamel dial representing North America, sold for SFr. 1'433'500 (US$ 950,000/UK£ 561,276) - Overall WORLD RECORD; and a WORLD RECORD for a Ref. 2523 in PINK gold with cloisonne enamel dial. ? Antiquorum, New York, June 20, 1998, Lot 140: PINK gold wristwatch, Ref. 2523-1, made in 1965, with guilloche dial, on silver dial plate, sold for US$ 662,500 (Sfr. 987'000) - WORLD RECORD. ? Antiquoruu, Geneva, October 21-22, 1995, Lot 918: WHITE gold wristwatch, Ref 2523, circa 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 clial, on silver dial plate, solcl for UK£ 293,000 (SFr. 721'512/US$ 492,240) - WORLD RECORD The NEXT HIGI-LEST PRICE, for this exact type of wristwatch, was realized by Antiqurom, New York, on dune 20, 1998, lot 497, at US$ 332,500 (Sfr: 495'500). ? Sotheby's, New York, March 9, 1998, lot 193: YELLOW gold wristwatch, Ref. 2523, circa 1953, with guilloche clial, on gold dial plate, sold for US$ 420,000 (SFr. 625'000) - WORLD RECORD ? Antiquorum, Geneva, April 12-13, 1997, lot 600: YELLOW gold wristwatch, Ref. 2523, made in 1953, with blue translucent enamel dial, solcl for SFr. 652'500 (US$ 456,300) - WORLD RECORD ? Antquorumh, Geneva, April 9, 1989, " Me t of Patek Philippe'; lot 294: YELLOW gold wristwatch, Ref 2523, circa 1955, with cloisonne enamel clial representing North America, sold for SFr. 396'000 ( US$ 240,000) - WORLD RECORD This result was exceptional An the time but should such a watch cone to auction nowadays it would more than likely realize over twice that figure.