Swiss lever tourbillon watch with Guillaume balance Circa 1951

Gold open faced lever tourbillon watch by Patek Philippe
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An extremely fine and rare Swiss 18 carat gold open faced keyless lever tourbillon watch with Guillaume balance, (encased in) circa 1951. Nickel finished lever movement engraved HOX (manufactured in 1930), numbered twice and stamped twice with the Geneva seal, 18 jewels, Guillaume balance with gold poising screws, polished steel three armed one minute tourbillon cage by Hector Golay, central jewel set in gold screwed chaton, blued steel hairspring. Hinged gold cuvette. Silvered matte dial, applied gold Breguet numerals, gold feuille hands, outer silvered dot minute divisions and subsidiary seconds. Plain case with hidden hinges. Case, cuvette, dial and movement signed, case and movement numbered. Comes with a Bulletin d’Observatoire.
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Diameter: 48.2 mm
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Signed: Patek Philippe & Cie Genève