Rare and important 18k gold complicated watch Circa 1917

Gold open faced complicated watch by  Patek Philippe
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A rare and important Swiss spl18 carat gold open faced minute repeating perpetual calendar split seconds chronograph keyless lever watch with half instantaneous thirty minute recorder and moon phases, circa 1917. Mechanical lever movement, 40 jewels, bimetallic compensation balance, swan neck regulator, wolf’s tooth winding, repeating on two polished steel hammers onto two gongs, activated through a slide in the band. Gold cuvette. White enamel dial with Breguet numerals, outer Arabic five minute divisions, blued steel spade hands, four subsidiary dials for day and month in English, date combined with constant seconds, 30 minute register combined with phases of the moon and lunar calendar. Heavy case with hidden hinges, split seconds chronograph mechanism operated through the crown and through a button in the band, locked by a sliding lever in the band. Case, bow, dial and movement signed, cuvette numbered.
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Diameter: 54 mm
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Signed: Patek, Philippe & Co Geneva Switzerland