Pocket chronometers by Patek Philippe are extremely rare. An almost identical watch, No. 90538, is described and illustrated by Martin Huber & Alan Banbery in Patek Patek Philippe Pocket Watches, 1993 Edition, p. 170, fig. 136 a,b.Patek Philippe and ChronometryThe first rate trials for watches at the Geneva Observatory were carried out as early as 1790 and 1792, but until 1873, they were sporadic affairs and of no significance. Towards the second half of the 19th century, it was realised that the adoption of its own internationally recognised testing standard, could be a positive influence on the watch industry of the Canton of Geneva. And so, in 1873, the first annual chronometer competition at the Geneva Observatory was organised.According to Messrs. Alan Banbery & Martin Huber in Patek Philippe Pocket Watches, 1993 Edition, p. 85, the archives reveal that Patek Philippe & Co., won the series prize for the five best watches as early as 1884 and 1895, with 184,9 and 230,14 marks respectively. In the period between 1900 and 1939, the firm took 764 prizes for results achieved at the Geneva Observatory, of which 187 were first places. This represented over half of the total number of distinctions awarded. From 1943 to 1966,atek Philippe & Co., every year, entered watches for the contest at the Observatory, in the four following categories:- categorie A Deck watches 19''' to 31''' (43 to 70 mm).- categorie B Large pocket watches 17''' to 19''' (48 to 43 mm).- categorie C Small pocket watches 13.5''' to 17''' (30 to 38 mm).- categorie D Wristwatches and miniature watches.Part of these watches were fitted with a regular mechanical movement, the movement of the others being with a tourbillon regulator. The results of the contests were as follow: Movements with Simple Tourbillon Movements- categorie A 236 3- categorie B 51 18- categorie C 19 58- categorie D 27 480Total 333 559Watches from Patek Philippe & Co. also participated with great success in the competitions held at the Kew-Teddington Observatory. In 1904 one such watch was awarded the second place with 93 marks, and in 1907, the firm ran off with the first, second, sixth, seventh, eighth and ninth place. Watches from Patek Philippe & Co., won first place twice more when competing before the Second World War, namely in 1908and 1937.