Swiss silver military chronograph pocket watch Circa 1920

Silver watch made for the U.S.A. Corps of Engineers
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A Swiss silver keyless military chronograph pocket watch by Vacheron Constantin, Geneva, circa 1920. Made for the U.S.A. Corps of Engineers. Polished case back, made by Huguenin Frères, Le Locle. The case back of this watch is not engraved with the military texts usually found on objects of this kind. It is reasonable to assume that this watch was not allocated to a soldier but remained in the American Expeditionary Forces inventory.
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A 1/5 second chronograph, activated by the round push piece located on the winding crown. White enamel dial with suspended Arabic numerals, with the mention Corps of Engineers – U.S.A., subsidiary seconds at 6 and blued steel skeleton hands. A gilded brass movement with going barrel, straight line lever escapement, cut bimetallic compensated balance with gold poising screws and blued steel hairspring with terminal curve, polished steel index regulator with swanneck spring and micrometric screw. The dial, case and movement are signed.
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Diameter: 51 mm
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Weight: 86 g
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Signed: Vacheron Constantin  Geneva
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Corps of Engineers, U.S.A.
In 1918, several Swiss horological manufacturers (Vacheron Constantin, IWC, Ulysse Nardin, etc.) started the production of pocket watches, with or without chronograph, intended for the “Corps of Engineers” of the United States Army. Following the U.S. entry into the war in 1917, the Americans set up a purchasing office for equipment for their expeditionary forces, the American Expeditionary Forces, which ordered several thousand watches until 1920. Especially designed for engineers, they are made of stainless steel, withstand temperature differences and have luminescent numerals and hands.