Swiss gold full hunter watch for the American market Circa 1886

Gold hunting cased pocket watch by Vacheron & Constantin
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A Swiss 18K yellow gold hunting cased keyless lever pocket watch made for the American market, circa 1886.
White enamel dial with suspended fancy black Arabic hours, an outer minutes track with red Arabic five-minute numerals, subsidiary seconds at 6 o’clock and original pear hands. The round-shaped engine-turned case is made by H.O. & Co, U.S.A., both sides engraved in taille-douce, the case back with a heron, on the inside of the front cover an escutcheon with the cypher NRT, the band guilloché. Rhodium-plated movement, going barrel, straight-line equilibrated moustache lever escapement, cut bimetallic compensated balance with gold poising screws, patented index regulator with micrometric screw, adjusted, protected on the inside with a soft iron ring against magnetic fields. Dial, case and movement signed. Accompanied by a Vacheron & Constantin token, an illustrated paper and a copy of the invention patent.
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Diameter: 54 mm
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Signed: Vacheron & Constantin Geneva
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The movement is based on the American invention patent No. 291 780, delivered on January 8th, 1884, to Ernest-Jacques Roux and Louis-Uriel Fatio in Geneva, for a watch regulator (a precision regulating device for fast/slow using a micrometric screw).