Rare English silver observatory pocket watch Circa 1890

Silver open faced pocket watch
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Very rare observatory watch with split seconds chronograph and 60-minute register, signed by Smith & Son London, circa 1890.
A solid silver cased, lever movement, split-seconds chronograph, signed on the cage, original enamel dial, time display on the upper side, 60-minute-register on the left, subsidiary seconds on the right, blued steel hands, good condition of preservation, very rare.
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Diameter: 54 mm
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Weight: 138 g
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Signed:  Smith & Son  London