Unusual Swiss open faced lever deck chronometer Circa 1961

Silver deck watch with Guillaume balance, power reserve and break circuit 
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An unusual Swiss silver open faced keyless lever deck chronometer with Guillaume balance, power reserve and break circuit, circa 1961. Gilt finished fully jewelled lever movement, Guillaume balance with gold poising screws, cam wheel regulator, escape wheel pinion fitted with a cam for contact breaking each second. Silver cuvette. Silvered matte dial and Roman numerals, blued steel spade hands, two subsidiary dials for 36 hours power reserve and constant seconds. Large water resistant type case, screw back, a sliding lever for the hack feature and transmitting pin in the band, large ball form crown, in three tier lacquered mahogany box with integrated power supply and conductors. Case, cuvette, dial and movement signed and numbered. Comes with original Bulletin de Marche and wooden box.
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Diameter: 64.5 mm
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Signed: Ulysse Nardin Locle Suisse Chronometre 128006