This watch, the very first wristwatch of this series, Ref. 2526, and also, the first self-winding wristwatch ever made by Patek Philippe is illustrated in Collecting Patek Philippe Watches by Madeleine and Osvaldo Patrizzi, Guido Mondani Editore, Genova, 1994, p. 111, pl. 167. Ref. 2526 First launched by Patek Philippe in 1953, the first self-winding wristwatch model ever made by the House, with the calibre 12 " '-600 AT, bearing the serial number 760000. It would appear that Patek Philippe produced the Ref. 2526 in 580 examples, mostly with enamel dial. - 20 examples in platinum. - 30 examples in pink gold. - 50 examples in white gold. - 480 examples in yellow gold. The Ref. 2526 is a most appealing wristwatch and highly sought after by collectors. There have been four generations of this model which have evolved as follows: - 1st generation: domed screw back, synthetic beige enamel dial with applied indexes. The enamel is flared around the holes which hold the indexes, the central hands and the subsidiary seconds hand. - 2nd generation: domed screw back, synthetic beige enamel dial with applied indexes. The indexes are inlaid in the enamel surface; the enamel is flared around the holes which hold the central hands and the subsidiary seconds hand. In this particular series, only very few examples were made with black dial and even fewer with Breguet numerals. - 3rd generation: identical to the 2nd generation but with practically flat screw back. Very few examples of this series were produced with black dial, and only one with black dial and Breguet numerals is known to date. - 4th generation: practically flat screw back, synthetic beige enamel dial with applied indexes. The indexes are luminescent and inlaid in the enamel surface; the enamel is flared around the holes which hold the central hands and the subsidiary seconds hand.