Swiss gold chronograph watch with pulsometer scale Circa 1915

Gold chronograph watch with pulsometer 
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An extremely rare Swiss 18 carat gold open faced pocket chronometer with pulsometer and chronograph made by Vacheron & Constantin in Geneva, circa 1915. A numbered polished case. Signed white enamel dial with bold Roman hours, an outer minute and fifth of a second track with Arabic five minute numerals, outermost red pulsometer scale, subsidiary seconds at 6 o’clock and blued steel hands. Signed and numbered movement with a special anchor chronometer escapement, an extremely large balance, 20 jewels and a column wheel chronograph.
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Diameter: 51 mm
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Weight: 91 g
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Signed: Vacheron & Constantin Genève Suisse