Swiss open faced deck watch with split seconds Circa 1940

Deck watch in a mahogany box
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A fine and rare Swiss, Staybrite, keyless circuit breaker lever chronometer deck watch, circa 1940. With a split 10th of a second chronograph, instantaneous 15 minute register and original mahogany three tier deck box with electrical contacts. A  polished, insulated electrical contact in the band at 9 o’clock. Hinged cuvette. White enamel dial, bold Arabic numerals, outer minute track, outermost fifths of second divisions and Arabic three second numerals, subsidiary seconds at 6, instantaneous 15 minute register at 12. Blued steel spade hands.

A rhodium-plated movement, Geneva striping decoration, 28 jewels, fast beating straight-line lever escapement, cut bimetallic compensation balance, Breguet balance spring, swan neck micrometre regulator, the escape wheel arbor is fitted with a cam allowing for breaking electrical contacts every fifth of a second via a lever activated by a bolt at 6 o’clock. Dial, case and movement signed.
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Diameter: 64 mm
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Signed: Ulysse Nardin Locle & Genève
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The present watch is calibrated so that 30 seconds are recorded in one revolution of the chronograph hand instead of the usual 60 seconds. This is achieved by a fast beating escapement; the hour and minute hands are geared to operate in the usual manner. This chronograph was specially made to time events to a precision of 1/10 second.