Very rare German 18K gold open face virgule watch Circa 1800

Rose gold virgule pocket watch
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A very rare German 18 carat rose gold open faced virgule pocket watch, circa 1800. Full plate movement, virgule escapement, three-arm copper balance. White enamel dial with Arabic hours, outer minute divisions with gold five-minute indexes and hands with gilt tips. Plain case. Dial and cuvette signed.
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Diameter: 53 mm
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Weight: 124 g
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Signed: J.C. Maßmann à Berlin