Mysterious Swiss silver keyless cylinder pocket watch Circa 1890

Silver mystery watch glazed on both sides
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A rare Swiss, silver keyless mystery pocket watch, circa 1890. A polished case, glazed on both sides. Eccentric glass dial with silver painted radial Roman numerals and outer minute track, engine turned dial plates decorated with a star pattern. Blued steel spade hands. Gilt brass movement, crescent shaped, 10 jewels, cylinder escapement, plain brass three arm balance, flat balance spring, index regulator.
Signed on the dial plate by the maker.
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Diameter: 54 mm
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Signed: A.S. & F. Armand Schwob & Frère  Le Chaux-de-Fonds