Impressive Swiss 18K gold Chronomètre Royal Circa 1910

Gold ankerchronometer by Vacheron & Constantin
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An impressive, keyless-winding, Swiss 18-carat gold ankerchronometer pocket watch, Chronomètre Royal, with open face, circa 1910.
Round-shaped 18-carat yellow gold case. Case back guilloché with a sunray motif. Enamel dial with Arabic numerals, outer minutes track, subsidiary dial for the seconds, and gold spade hands. Gilded brass movement with going barrel, gold screwed chaton (setting) on the central wheel, straight-line lever escapement, compensated balance with gold poising screws and blued steel hairspring with a terminal curve, index regulator with swan-neck spring, and micrometric screw. Dial, case and movement signed. Accompanied by original fitted box and certificate of origin.
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Diameter: 57 mm
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Weight: 133 g
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Signed: Vacheron & Constantin Genève Chronomètre Royal