Swiss 18k gold keyless Adjusted Extra lever watch Circa 1893

Gold open-faced lever chronometer by Patek Philippe
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A very fine and rare Swiss 18-carat gold open-faced keyless Adjusted Extra lever chronometer pocket watch with Guillaume balance and Geneva Observatory Rating Certificate Grade A obtained on February 20, 1896. Retailed by Tiffany & Co, New York, 1893. Sold on May 9, 1896. Nickel-silver Extra movement, Geneva striping decoration, engraved twice with the movement number, 17 jewels, wolf’s tooth winding, straight-line counterpoised and calibrated lever escapement, anibal-brass Guillaume balance with winged arms, gold temperature and meantime adjustment screws, blued steel Breguet balance spring with terminal curve, diamond endstone, swan-neck micrometer regulator also with additional fixed index arm and engraved scale on the center bridge. Gold hinged cuvette engraved Harrison L. Beatty from Uncle Joseph Bush, Dec. 4th, 1896. White enamel dial with Breguet numerals, outer minute track, subsidiary seconds dial, and original blued steel spade hands. Polished case, concealed hinge. Dial, case and movement signed Tiffany & Co New York, case and movement numbered. Accompanied by the Extract from the Archives.
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Diameter: 53 mm
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Signed: Patek, Philippe & Cie Genève
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The two regulator arms do not work independently but are fixed in position, the regulation is adjusted using the familiar ‘swan neck’ regulator, the other arm showing the degree of regulation. When destined for Observatory Timing Contests, the movements of Patek Philippe watches, like those of other makers, were double engraved with serial numbers. The inscription ‘Extra’ on the bridge of the movement refers to the high finishing of all the parts of the movement.