Swiss gold and rose cut diamond set pocket watch Circa 1905

Gold chronograph with a telemeter scale 
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A Swiss 18 carat rose gold and rose cut diamond set open faced keyless pocket watch by Vacheron Constantin, Geneva, circa 1905. With a chronograph and telemeter scale. Back cover with an applied foliate gold monogram ‘’DG’’ set with rose cut diamonds. White enamel dial with Arabic numerals, outer minute track, subsidiary seconds at 6 and gold hands. A frosted gilt movement, 23 jewels, straight line lever escapement, cut bimetallic compensation balance, blued steel Breguet balance spring, index regulator, visible chronograph work. Dial, case and movement are signed.
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Diameter: 51 mm
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Signed: Vacheron Constantin  Geneva
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Accompanied by an original Vacheron Constantin box.
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Telemeter: Using a telemeter scale, it is possible to measure the distance of a phenomenon which is both visible and audible. The chronograph is started as soon as the phenomenon is seen and is stopped when the sound is heard. The position of the hand on the scale then shows the distance in kilometres or miles separating the phenomenon from the observer. The calibration is based on the speed with which sound travels through air – approximately 340 metres or 1,115 feet per second.