Possibly unique chronograph, telemetre scale Circa 1939

Rose gold open faced lever chronograph by Patek Philippe
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A rare and attractive, possibly unique Swiss 18 carat rose gold open faced keyless lever chronograph watch with telemetre scale, circa 1939. Nickel finished lever movement, 23 jewels, bimetallic compensation balance. Silvered matte dial, applied rose gold baton and Arabic numerals, outer railway five minute divisions and telemetre scale, two subsidiary dials indicating 30 minutes register and constant seconds. Plain case, snap on back. Case, dial and movement signed.
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Diameter: 46 mm
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Signed: Patek Philippe & Co Genève