Swiss yellow gold complicated pocket watch Circa 1920

Gold open faced lever by Longines
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A fine and rare, keyless, 18K yellow gold pocket watch by Longines, circa 1920. With square button split-seconds chronograph, instantaneous 30-minute register, tachometer and telemeter. Solid case, polished, hinged cuvette engraved with various Longines Grand Prix award medals, split seconds push button on the case band. White enamel dial with bold painted Arabic numerals, outer Arabic minute and chronograph divisions, outermost tachometer and telemeter graduation to 1000 m., subsidiary dials for the seconds and the 30-minute register. Blued steel Breguet hands, rhodium plated, 21 jewels, straight line lever escapement, monometallic balance with screws, Breguet balance spring, visible split seconds mechanism. Dial, case and movement are signed.
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Diameter: 52 mm
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Signed: Longines  Swiss