Important Swiss 18K gold open faced complicated watch Circa 1900

Gold gentleman’s watch with complications
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An important Swiss 18 carat gold open faced quarter repeating lever pocket watch with perpetual calendar and moon phases, circa 1900. White enamel dial with Roman hours, an outer minute track, Arabic five minute numerals, subsidiary dials for the months of the year including leap year at 12 o’clock, the days of the week at 9, date indication at 3, auxiliary seconds with concentric phases of the moon at 6 and black spade & whip hands. Dial signed, case numbered.
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Diameter: 52 mm
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Weight: 122.5 g
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Signed: Cosandier Frères & Co