Unusual French 18 carat gold pocket chronometer Circa 1867

Chronometer with Fahrenheit and Centigrade thermometer by Boitel
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A fine, rare and unusual French 18 carat gold open faced keywound pocket chronometer with Fahrenheit and Centigrade thermometer, circa 1867. Nickel movement, exposed fusee and chain with Harrison’s maintaining power, gold train, jewels in screwed gold chatons, gold wheel train, Earnshaw type chronometer escapement with spring footed detent, jewelled locking stone, cut bimetallic compensation balance with gold elliptical weights, mean time adjustment nuts and peripheral temperature adjustment screws, blued steel helical balance spring with terminal curve and adjustable stud mounted to a special slide for minute adjustment, diamond endstone, index regulator. Case polished, engine-turned inside back cover and cuvette. Hinged gold cuvette.
White enamel dial with Roman numerals, aperture at 12 o’clock revealing the thermometer mechanism, calibrated for 0 to 100 Fahrenheit and -20 to +40 Centigrade, subsidiary seconds. Plain case. Movement signed.
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Diameter: 50 mm
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Signed: Hri Boitel Paris Exp.tion Universelle de 1867 Chronomètre
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This watch was exhibited at the Paris Universal Exhibition of 1867. The Exhibition was Napoleon III?s answer to the London 1851 Exhibition, to demonstrate to the world that France was an industrial and technical power in its own right.