German 56h power reserve chronometer Circa 1923

Deck chronometer by Lange & Söhne
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A very rare German 56-hour power reserve marine chronometer, one of only 46 made Sidereal Time watches, circa 1923. Spring detent chronometer movement, helical hairspring. Silvered dial with Roman hours and outer minute divisions, subsidiary seconds, 56-hour power reserve indicator, gold hands, regulated to sidereal time. Three-part mahogany box, brass case, gimbal suspension. Box and dial signed and numbered, case and movement with matching numbers. Comes with an Extract from the Archives and the original key.
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Dimesions: 18 × 18 × 18 cm
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Signed: A. Lange & Söhne Glashütte B/Dresden