Unique Swiss gold open faced complicated watch Circa 1951

Repeating chronograph with perpetual calendar and moon phases
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An extremely fine, slim and unique Swiss 18 carat gold open faced minute repeating split seconds chronograph keyless lever watch with perpetual calendar and moon phases, circa 1951. Retailed by Gübelin. Nickel finished lever movement, 36 jewels, bimetallic compensation balance, micrometer regulator, minute repeating on two polished steel hammers onto two gongs. Silvered dial with applied gold Roman numerals, inner railway five minute divisions, four subsidiary dials for month and leap year indicator, day, date, constant seconds and moon phases. Plain case, stepped bezel, repeating slide in the band, snap on back, split seconds chronograph mechanism operated through a button in the band and through the crown. Case signed by retailer and numbered, dial signed by watchmaker and retailer, movement signed by watchmaker and numbered. Comes with box.
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Diameter: 52 mm
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Signed: Audemars Piguet Genève