Swiss pentagonal open faced anniversary watch Circa 1924

Platinum lever by Gruen
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A fine Swiss platium pentagonal open faced keyless anniversary pocket watch, circa 1924. 12 Carat gold Extra Precision lever movement, bridges engraved overall with foliate scrolls, 21 jewels and 2 diamonds, bimetallic compensation balance, precision regulator. Silvered dial, applied Arabic numerals and engine turned subsidiary seconds. Pentagonal shaped case, black enamel geometric motif to the bezel, back rim and bow, engraved band, engraved snap on back. Dial and movement signed.
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Diameter: 46 mm (at widest point)
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Signed: Fiftieth Anniversary Gruen Switzerland