French brass 42 hour going marine deck chronometer Circa 1860

Deck chronometer with pivoted detent escapement
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A French brass 42 hour going marine deck chronometer with power reserve indicator, circa 1860. A rosewood box with brass corners fixings and sunk brass handles, the glazed upper section with a hinged lid and brass corners. Brass bowl and gimballed suspension. Silvered dial with Roman numerals, subsidiary seconds and Up and Down scale. Blued steel Breguet hands. Spotted brass, full plate movement with cylindrical pillars secured by screws, the back plate relieved for the barrel, fusee with chain and maintaining power, Earnshaw type spring detent escapement, two arm balance with cylindricaweights and timing screws. Free sprung blued steel helical balance spring with terminal curves.
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Diameter: 75 mm
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Box: 165 x 165 x 165 mm
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Signed: Auguste Berthoud  Paris
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Accompanied by a rosewood box