Swiss lever chronometer with unusual movement Circa 1883

Gold open faced pocket chronometer by Patek Philippe
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A very rare Swiss 18 carat gold open faced lever pocket chronometer with unusual movement, circa 1883. Ankerchronometer movement, very large chronometer balance, unusual main plate, very long regulator pointer, very rare Patek Philippe calibre. White enamel dial with Roman hours and Arabic five minutes, subsidiary seconds, rose gold hands. Plain case, monogram on the back. Dial signed, movement signed and numbered, cuvette signed and numbered, case numbered, movement number also on the case.
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Diameter: 48 mm
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Weight: 85 g
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Signed: Patek, Philippe & Cie Genève