Swiss pocket watch with patented micrometric regulator Circa 1900

Open faced pocket watch by Vacheron & Constantin
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A very fine Swiss 18 Carat pink gold keyless winding pocket watch with open face and patented micrometric regulator, circa 1900.
Gilded brass movement, going barrel, straight line equilibrated lever escapement, compensated balance with gold poising screws and blued steel hairspring with a terminal curve, patented index regulator with a micrometric screw. Enamel dial with Roman radial hours, outer minutes track with Arabic five minutes numerals, subsidiary dial for the seconds, and original gold pear hands. Round shaped 18 Carat pink gold case. Accompanied by a contemporary 18 Carat yellow gold chain (length 380 mm. approx).
Dial, case and movement signed.
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Diameter: 49 mm
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Signed: Vacheron & Constantin, Genève
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Movement-based on the American invention patent No. 291 780, delivered on January 8, 1884, to Ernest-Jacques Roux and Louis-Uriel Fatio, Geneva, for a watch regulator (precision regulating device for fast/slow using a micrometric screw).