Rare Swiss chronograph for car racing purposes Circa 1920

Gold hunting cased repeater by LeCoultre & Cie.
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A rare Swiss minute repeating hunting cased pocket watch with chronograph, and a 30-minute counter and concentric tachy scale, to be used for car racing purposes, circa 1920.
18-Carat gold, polished, à goutte case, pusher for chronograph at 12, slide for repeating mechanism, and a numbered and signed gold dome, with engraving: F. Senn, Boul. St. Denis, Bâle & Paris, Importé de Suisse. Signed enamel dial with Arabic numerals, auxiliary seconds, concentric blue/red tachy scale, and blued spade hands. Bridge movement, rhodium-plated, Geneva Stripes decoration, mirror-polished and bevelled chronograph steel parts, ratchet wheel, two hammers / two gongs, governor for repetition, wolf-teeth winding wheels, and gold screw compensation balance.
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Diameter: 54 mm
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Weight: 130 g
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Signed: Auto Sport Senn