Swiss mystery watch made for the Chinese market Circa 1890

Glazed both sides cylinder watch
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A fine and very rare Swiss, 18 Carat gold keyless mystery pocket watch, circa 1890. Retailed by J. Ullmann, Chaux-de-Fonds, Hong Kong & Shanghai. Made for the Chinese market. A polished case, glazed on both sides. Eccentric glass dial with painted radial Roman numerals and outer minute track, engine turned dial plates. Black spade hands. Gilt brass movement, crescent shaped, ten jewels, cylinder escapement, plain brass three arm balance, flat balance spring, index regulator.
Signed on the dial plates by the maker and retailer.
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Diameter: 54 mm
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Signed: Armand Schwob & Frère  La Chaux-de-Fonds
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The case is slightly worn.
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Built on the principle invented by Robert-Houdin for clocks, this watch appears to work without any mechanical movement. It is, in fact, driven by the crescent shaped movement concealed above the dial in the border, the hands revolving along with the glass plate set beneath the dial. Patented by Armand Schwob & Frère in Paris on 24 January 1889, such watches were very popular towards the end of the 19th century.