French 18K white gold keyless mystery dress watch Circa 1980

White gold watch with matching Cartier long chain
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A very fine, elegant French, 18K white gold, keyless, mystery dress watch, circa 1980. Accompanied by the original matching heavy 18K white gold Cartier long chain. Made in a limited series. A polished case with an eccentric aperture for the mystery hands with brushed chapter ring with champlevé Roman numerals, inner minute track, triangular swivel bow. Blued steel Breguet hands. Square rhodium-plated movement with canted corners, 34 x 34 mm, Geneva striping decoration, 17 jewels, straight-line lever escapement, monometallic balance with self-compensating flat balance spring, Incablock shock absorber on both balance pivots, aperture below the train for sapphire discs holding the hands. Case and movement signed.
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Diameter: 50 mm
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Signed: Cartier  Paris
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The idea for this type of mystery mechanism originated with Armand Schwob & Frère à Paris and was patented on 24 January 1889. Cartier improved upon the idea, employing a large, high-quality movement with an excentric opening. Cartier made very few of these watches.