Swiss gold chronograph and tachometer watch Circa 1911

Gold Chronomètre pocket watch by Vacheron & Constantin
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An attractive and extremely rare Swiss keyless-winding pocket watch, model chronomètre, with chronograph and tachymetric scale, circa 1911. This watch was completed in 1925 and sold on February 23, 1931, to Mr F. Chiappe (Italy).
Polished 18K yellow gold round-shaped case. Enamel dial with Arabic numerals, original pear hands, subsidiary dial for the constant seconds, outer minute and second track, and outermost blue and red tachymetric scale graduated for 1000 metres. Lever escapement, index regulator with swan-neck spring and micrometric screw, adjusted by Edmond Olivier. Dial, case and movement signed.
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Diameter: 52 mm
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Signed: Vacheron & Constantin, Genève Suisse
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Accompanied by a copy of the Bulletin de Marche of the Astronomical Observatory of Geneva (dated September 20, 1994), and by the Extract from the Archives, dated November 10, 1994, that mentioned that this watch was made in 1911 and sold in 1931.