Poinçons de GenèveThe voluntary quality control of watches at the Geneva Observatory, was established by a law dated November 6, 1886. Conditions were laid down for the attribution and stamping of the Poinçons de Genève, punch-marks designed as the coat-of-arms of Geneva. Pocket watches, or wristwatches which carry the Poinçons de Genève, considered as an equivalent to a Bulletin Officiel de Marche, punched on a bridge and on the main plate of the movement, were qualified to be officially termed ?chronometers?.Ref. 2526First launched by Patek Philippe in 1953, the first self-winding wristwatch model ever made by the company, with the calibre12???-600 AT, bearing the serial number 760?000.It would appear that Patek Philippe produced the Ref. 2526in 580 examples, mostly with enamel dial.- 20 examples in platinum.- 30 examples in white gold.- 50 examples in pink 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.The very first wristwatch of this series, Ref. 2526, being also, the first self-winding wristwatch ever made by Patek Philippe, is illustrated in Collecting Patek Philippe Watches, by Madeleineand Osvaldo Patrizzi, Guido Mondani Editore, Genova, 1994,p. 111, pl. 167.This watch was sold by Antiquorum in New York on June 20, 1998, lot 133, for US$ 57,500.Similar watches are published in Patek Philippe Wristwatches, by Martin Huber & Alan Banbery, 1998 Edition, pp. 213-214and 216-217.According to our records, only 7?100 movements Cal. 12???-600 AT have been made from 1953 to circa 1959 and were mounted in wristwatches bearing the references 2526, 2540, 2551, 2552, 2583, 2584, 2585, 3403, 3415, and 3425. From 1959, Ref. 3415, 3425, 3428, 3429, 3433, 3443, 3435, 3438, 3439, 3440, 3441, 3444 and 3454 were equipped with Cal. 27-460 as well.Cal. 27-460 became the movement which was used for all automatic wristwatches and 27-460 Q for perpetual calendar wristwatches with automatic winding.Circa 1960, Ref. 2526 was equipped with Cal. 27-460, the latest automatic movement by Patek Philippe at the time and became the Ref. 3428.Ref. 3428Production of this reference started in 1960.The calibre 27-460 marks the end of the production of watches with enamel dials, circa 1960. Very few watches with this combination exist.One of these watches is published in The Legendary Watches from Patek Philippe?s Private Watch Museum, Musée de l?Horlogerie et de l?Emaillerie, Genève, April 10-September 30, 1989, Geneva 1989,p. 22, pl. IX, No. 391.