Swiss silver observation watch with 40h power reserve Circa 1919

Silver open faced lever watch
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A large Swiss silver open faced observation watch with 40 hour power reserve made by Vacheron Constantin SA in Geneva, circa 1919. The ¾ plate movement with a piston tooth lever escapement and Guillaume gold screw compensation balance. Silvered dial with Roman hour numerals, an outer minute track, subsidiary seconds at 6 o’clock, a power reserve indicator at 12 and blued heavy spade hands. The plain case is glazed on both sides. Dial signed, movement signed and numbered. Comes with an Extract from the Andreas Hiddings Chronometer database.
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Diameter: 64 mm
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Weight: 190 g
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Signed: Vacheron & Constantin Genève Suisse
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In 1919, this watch participated in the chronometer competition of the Geneva Observatory in the category “1st Class Chronometers – Honourable Mention”, achieving a score of 711 points and placing 29th out of 81 chronometers.
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Furthermore, in 1919/1920, this piece participated in the chronometer competition at the National Physical Laboratory in Teddington in the category “Kew – Class A” and was awarded “especially good.”