American gold diamond-set lady’s pendant watch Circa 1890

Gold, diamond-set watch with brooch 
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A very fine, rare and unusual American, 18K yellow gold and platinum, miniature, lady’s keyless pendant and brooch watch, circa 1890. The diamond-set detachable heart-shaped outer case and detachable diamond-set coronet brooch fitting. A heart-shaped case, pierced and set with 93 round diamonds. The back cover engraved with a monogram, trefoil bow set on both sides with diamonds. Coronet brooch fitting set with 58 round diamonds. White enamel dial with radial Roman numerals, outer minute track. Blued steel spade hands. A rhodium-plated movement, Geneva striping decoration, 17 jewels, straight-line lever escapement, cut bimetallic compensation balance, blued steel flat balance spring, index regulator. Dial, case and movement signed.
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Diameter: 26 mm
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Signed: Tiffany & Co.  New York