French gold 24 hours World Time pocket watch Circa 1899

Gold single handed pocket watch
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Extremely rare French, 18 carat yellow gold single handed 24 hours World Time pocket watch, circa 1899. A keyless pocket watch with a world planisphere enamel dial with longitudes and latitudes, day and night indication and single hand making one revolution in 24 hours. Accompanied by a fascinating collection of hand written documents by Callier dated 1894, describing his thoughts on technical aspects of watchmaking.
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A polished case with a hinged gold cuvette. White enamel dial with radial Roman numerals 1-XII twice for 24 hours, days in red, nights in black, outer dot minute divisions with five minute Arabic numerals, centre with revolving enamel disc painted with the northern hemisphere. Blued steel single baton hand making one revolution in 24 hours. Frosted gilt movement, 15 jewels, wolf’s tooth winding, straight line calibrated lever escapement, cut bimetallic compensation balance with Breguet balance spring, index regulator. Cuvette signed.
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Diameter: 50 mm
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Signed: B. Callier  Paris
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Accompanied by a fascinating collection of hand written documents
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B. Callier, son of Filleul Charles Bernard Garnier, Horloger de l’Observatoire, et de la Marine de l’Etat, Paris.
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The present watch is only the second of Callier’s Montre Geographique watches to appear at auction and the first example seen with a single hand. Callier was the successor of Winnerl, one of the best French Chronometer makers of the second part of the 19th century. The present watch shows longitude for world cities, latitude drawn on the map, and the time at any place on the planet – described by Callier Donnant les longitudes, les latitudes et heures de tous les points de la terre. The hand is set to the time at the home city, to read the time at any other world city, the longitude line is found and followed to the chapter ring where the corresponding time can be read. An ingenious invention, the planisphere enamel dial is particularly beautiful and detailed.