To the best of our knowledge, very few Réversible Patek Philippe writswatches were made in the 1930's.Only three examples of the gentleman's model, made in 1933, are known to exist:- No. 822399, case No. 609482, in 18K yellow and white gold,it was given as a gift by Charles and Jean Stern to an employee in commemoration of his 20 years of service, published in Patek Philippe Wristwatches, by Martin Huber & Alan Banbery, 1998 Edition, p. 111.- No. 823422, case No. 609483, in 18K yellow and white gold, retailed by Gübelin, Lucerne, sold by Antiquorum in Geneva, April 23, 1995, lot 619, for SFr. 110,000.- No. 823431, in 18K yellow and white gold, sold by Antiquorum in Geneva, March 24, 1985, lot 134.Only two examples of the lady's model, made in 1936,are known to exist:- No. 826097, published in Patek Philippe Wristwatches, by Martin Huber & Alan Banbery, 1998 Edition, p. 116.- No. 860396, case No. 609431, in 18K white gold, now offered for sale.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".