Rare German 18K gold open faced keyless lever watch Circa 1915

Gold open faced keyless lever by A. Lange & Söhne
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A very fine and rare German 18 carat gold open faced keyless lever pocket watch, circa 1915. Frosted gilt Glashütte ¾ plate movement, 17 jewels in screwed gold chatons, straight-line Glashütte lever escapement, gold pallet fork and escape wheel, banking with a pin and hole, Lange Guillaume-type balance with gold timing screws, blued steel Breguet balance spring with overcoil, the terminal stud adjustable by a screw, swan-neck micrometre regulator. Silver dial with champlevé Breguet numerals, outer minute track, subsidiary seconds, the centre with sunray engine-turning and original blued steel Breguet hands. Solid case, polished. Gold hinged cuvette. Dial, case and movement signed.
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Diameter: 51 mm
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Signed: A. Lange & Söhne Glashütte I/SA