Unusual Swiss 18 carat white gold chronograph Circa 1927

Lever chronograph by Audemars Piguet
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A rare and unusual Swiss 18 carat white gold open faced keyless lever chronograph watch, circa 1927. Nickel finished jewelled lever movement, bimetallic compensation balance. Silvered matte dial, offset baton numerals, outer enlarged railway minute divisions, semi circular blue scale calibrated for 200 units, two subsidiary dials for 60 minutes register and constant seconds. Case with ribbed bezel and rim, snap on back, chronograph button in the crown. Comes with an associated white gold, diamond set, black lacquer and velvet fob. Case, dial and movement signed.
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Diameter: 47 mm
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Signed: Audemars Piguet Genève