Unsigned chronograph with 30-counter and tachymeter Circa 1920

Gold chronograph with open face
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A golden chronograph with a rare dial, 30-minute counter and tachymeter, circa 1920.
Fine lever movement with column-wheel chronograph and counter. Enamel dial with multicoloured tachymeter scale (crackle in the edge area), 30-minute counter, Roman radial hours, Arabic 24-hour numerals, outer minutes/seconds track with Arabic five minutes/seconds numerals, subsidiary dial for the seconds, chronograph hand, and gold pear hands. Solid 18K gold polished quality case with case numbered.
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Diameter: 51 mm
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Weight: 87 g
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Unsigned