Swiss gold chronograph with tachymeter scale Circa 1934

Gold chronotachymeter
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A rare Swiss 18 carat gold open faced chronograph pocket watch with tachymeter scale made by Omega, circa 1934. The 4/5 plate movement with a piston tooth lever escapement and screw compensation balance. White enamel dial with black Arabic hour numerals, a minute track and fifth of a second divisions, concentric multi coloured tachymeter scale, 30 minute counter at 12 o’clock, subsidiary seconds at 6 and leaf hands. The plain case with a pusher for the chronograph in the crown. Dial signed, case and movement signed and numbered.
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Diameter: 50 mm
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Weight: 87 g
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Signed: Ω Omega Cadran Breveté S.G.D.G. Importé de Suisse
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The S.G.D.G. tachymeter dial allows one to measure any speed between 10.5 and 240 units without calculations. The 30 minute counter starts with five different coloured minute segments that indicate which colour of the spiral tachometer scale the speed can be read on.
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S.G.D.G. is short for Breveté Sans Garantie Du Gouvernement (patent without government guarantees).