French silver open faced cased lever deck watch Circa 1890

Silver lever by L. Leroy & Cie
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A large French deck watch – lever chronometer – with original box and additional blued hands, circa 1890.
Formerly with “Bulletin de Marche” of the Observatoire National de Besancon.
White enamel dial, black Roman numerals, black outer minute track, subsidiary seconds at 6, signed with L. Leroy & Cie.
Silver polished hinged open face case.  It has a 3/4 plate movement, a gold screw compensation balance, and hallmark “Viper”.
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Diameter: 62 mm
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Weight: 180 g
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Signed: L. Leroy & Cie., Horlogers de la Marine, 7 Bd de la Madelaine à Paris