Swiss gold perpetual calendar lever chronograph Circa 1880

Gold open faced chronograph with perpetual calendar by Patek Philippe
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A rare and early Swiss 18 carat gold open faced perpetual calendar keyless lever chronograph watch, circa 1880. Nickel finished jewelled lever movement, bimetallic compensation balance, wolf’s tooth winding. Gold cuvette. White enamel dial with Roman numerals, outer Arabic five minute divisions, three sunk subsidiary dials for day, date and constant seconds. Engine turned case back with engraved initials J.A.A.B., chronograph button in the crown, chronograph locking lever in the ribbed band. Case stamped and numbered, cuvette signed and numbered, dial signed.
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Diameter: 52 mm
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Signed: Patek, Philippe & Co Genève