French half hunter cased lever mystery dress watch Circa 1985

Platinum keyless half hunter by Cartier
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A very fine and very rare, elegant French platinum half hunter cased keyless lever mystery dress watch, made in a limited series in the 1980s. Montre Mysterieuse. Square movement with canted corners, rhodium plated, Geneva striping decoration, 17 jewels, straight line lever escapement, mono metallic balance, shock absorber, self compensating flat balance spring, aperture below the train for sapphire discs holding the hands. Transparent dial with sapphire crystals and original blued steel Breguet hands. Solid case, polished and brushed, off center aperture for the mystery hands with brushed chapter ring and engraved black radial Roman numerals, inner minute track, triangular swivel bow.
Case and movement signed, case numbered.
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Diameter: 50 mm
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Thickness: 8.5 mm
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Signed: Cartier Paris