Swiss keyless lever with 24-hour day and night dial Circa 1927

Silver and rose gold keyless lever watch 
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A fine and very unusual Swiss silver and rose gold open faced keyless lever pocket watch, circa 1927. Lever movement. White enamel 24-hour day and night dial with black Arabic hours 1-24, an outer minute track with red Arabic five-minute numerals, on the right an inner red Arabic scale from 1 to 12 and small subsidiary seconds, the hour hand making one full rotation in 24 hours. Plain case. Dial, case, cuvette and movement signed, the case with Swiss and German silver marks, case and movement numbered.
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Diameter: 51 mm
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Signed: Omega