Swiss silver lever chronometer navigation watch Circa 1921

Silver open faced lever pocket watch
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Exceptionally fine and rare, large, silver, keyless, extra adjusted lever chronometer navigation watch with Guillaume balance, circa 1921. Adjusted by J. Golay-Audemars, entered for Geneva Observatory Timing Contest, category A, in 1927, achieving 636 points and Honorable Mention. Accompanied by the Extract from the Archives and copy of the Observatoire de Geneve Service Chronometrique Register. Sold on January 30, 1942. A polished case, hinged silver cuvette. Brushed sand-coloured silver dial, champlevé Arabic numerals, outer minute track, subsidiary seconds. Blued steel Breguet hands.
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A rhodium-plated movement, Geneva striping decoration, pillar plate under the dial with oeil de perdrix finishing, 23 jewels, eight adjustments, very high-quality straight line calibrated equidistant lever escapement, Anibal-brass Guillaume compensation balance with poising wings on the balance arm, gold and platinum temperature and meantime adjustment screws, blued steel Breguet balance spring with inner and outer terminal curves, ruby banking pins in the shape of small plates inserted into the bridge, punched twice with Seal of Geneva Quality marks, swan-neck micrometric regulator, special mainspring ratchet wheel click preventing overwinding and Maltese Cross stop work. Dial, case and movement signed, case punched with Swiss and German silver marks.
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Diameter: 60 mm
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Signed: Patek Philippe & Cie.  Genève
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The present watch is a very fine example of a Patek Philippe navigation watch from a very small series, all destined for Observatory trials. The movement has the unusual winding click and Maltese cross stop work to prevent overwinding. It was submitted for trial at the Observatoire de Geneve in 1927, category A and the Bulletin de Marche was issued in March 1928, achieving the following results: 636 points out of a possible 1000 with honourable mention. It was tested with a compensation error by Centigrade degrees of 0.013, and reprise demarche of -0.40. It was adjusted by master régleur J. Golay-Audemars.
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The régleurs were the best-paid workers in the watch industry. Watches they adjusted, and particularly those awarded prizes at Observatory Contests, were several times more expensive than the regular production. When destined for Observatory Timing Contests, the movements of Patek Philippe watches, like those of other makers, were double engraved with the movement serial numbers. The inscription “Extra” on the bridge of the movement refers to the high finishing of all the parts of the movement. The case also bears a German import mark for silver indicating that it was sent for use by the German Navy. Very few navigation watches of this type were supplied by Patek Philippe, perhaps due to their high prices.