Swiss silver lever chronograph with tachymeter Circa 1920

Silver tachymeter chronograph by Vacheron & Constantin
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A Swiss silver open faced tachymeter chronograph in chronometer quality, circa 1920. Extremely rare calibre in chronometer quality, ankerchronometer with 20 jewels, rose gold wheels. White enamel dial with 30-minute register and tachymeter scale, blued steel hands. Plain case, Vacheron & Constantin punch. Dial signed, case and movement signed and numbered.
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Diameter: 52 mm
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Weight: 99 g
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Signed: Vacheron & Constantin Genève Swiss
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This chronograph is one of the rarest pocket chronographs produced by Vacheron & Constantin. Almost all Vacheron & Constantin chronographs have gold cases, except the military chronograph Corps of Engineers (U.S.A.). Civil Vacheron & Constantin chronographs with silver cases are hardly known, especially with this special chronometer calibre!