Rare French silver double-sided military chronograph Circa 1915

Silver chronograph military watch
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A rare French silver double-sided military chronograph to determine the distance of grenade impacts, circa 1915. Lever movement. Two white enamel dials, on one side an extremely rare chronograph with a special scale on which the distance of a grenade strike can very accurately be read, after the time of the strike is stopped. On the other side display of the time and two distance scales in scale 1: 80,000 and 1: 100,000, at which distances corresponding to a certain distance can be read, recorded by a wheel on the underside of the watch on a map. Plain case, winding crown with a compass.
Diameter: 51 mm
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Weight: 110 g
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Signed: No name