Rare Swiss 18k gold open faced complicated watch Circa 1931

Gold chronograph with perpetual calendar and moon phase by Patek Philippe
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A fine and rare Swiss 18 carat gold open faced minute repeating perpetual calendar split seconds chronograph keyless lever watch with moon phases, circa 1931. Mechanical movement, 41 jewels, bimetallic compensation balance, micrometer regulator, repeating on two hammers onto two gongs. Silvered dial, applied gold Arabic numerals, outer railway minute divisions, four subsidiary dials for month, leap year and 30 minutes register, day, date, constant seconds and moon phases, Plain case, snap on back, repeating slide in the band, split seconds chronograph button in the crown and in the band. Case, dial and movement signed, case and movement numbered. Comes with original box.
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Diameter: 50 mm
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Signed: Patek Philippe Genève