Swiss observation Greenwich Civil Time chronometer Circa 1940

Aluminium watch with a 24-hour dial by Longines 
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An absolute rare Swiss Greenwich Civil Time observatory chronometer with a 24-hour dial and 8-day movement calibre, circa 1940. The watch features an aluminium case with a screwed bezel and a 5-fold screwed back, although the latter is no longer original. The silver-plated 24-hour dial has an 8-day power reserve (192h), an outer minutes track, a subsidiary dial for seconds, and luminous steel hands. The movement is 24.41, with an 8-day power supply and special fine adjustment.
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Diameter: 80 mm
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Signed: Longines Wittnauer
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This clock is part of a chronometer set of 2 observatory chronometers, Greenwich sidereal time & civil time. In their original condition, both clocks were in a mahogany box.