Very fine and rare Swiss gold complicated watch Circa 1918

Gold open faced complicated watch by Patek Philippe
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A very fine and rare Swiss 18 carat gold open faced minute repeating perpetual calendar split seconds chronograph keyless lever watch with moon phases, circa 1918. Nickel finished lever movement, 35 jewels, bimetallic compensation balance, micrometer regulator, wolf’s tooth winding, repeating on two steel hammers. Gold cuvette, ivory coloured enamel dial with Roman numerals, outer Arabic five minute divisions, four subsidiary dials for moon phases and lunar calendar, day, month, date and constant seconds. Heavy case, hidden hinges, hinged back engraved L.R.M., repeating slide in the band, split seconds chronograph mechanism operated through the crown and through a button in the band, locked by a sliding lever in the band. Case, cuvette, dial and movement signed and numbered.
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Diameter: 54 mm
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Signed: Patek, Philippe & Cie Geneva Switzerland