English lever with tourbillon and power reserve Circa 1904

Gold tourbillon pocket chronometer with power reserve by S. Smith & Son
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A very fine and very rare English 18 carat gold open faced keyless pocket chronometer with one minute tourbillon regulator and 24 hour power reserve indication, Hallmarked London 1904-1905. Half plate movement, reversed fusee and chain, jeweled to the centre, one minute Nicole Nielsen equidistant arm tourbillon carriage, lateral polished steel bridge, English lateral lever escapement with lift on the pallets, cut bimetallic compensation balance with gold temperature and meantime adjustment screws, freesprung blued steel balance spring with double overcoiled Phillips outer terminal curve, pallet fork with unusual gold poising/calibrating screw. Gold hinged cuvette. Matte silver dial with champlevé Roman numerals, outer minute track, subsidiary seconds, 24 hour power reserve indicator below XII o’clock and blued steel spade hands. Solid polished case by Samuel Smith, mastermark SS, five bar hinge, swivel anti theft pendant. Dial and movement signed, case numbered.
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Diameter: 58 mm
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Signed: S. Smith & Son 9 Strand London Makers to the Admiralty and the Indian Government
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The watch employs a number of features assuring the most accurate timekeeping, the tourbillon regulator, averaging error, the freesprung double overcoiled balance spring which assures superior isochronism, the reverse fusee, first used by Mudge which lessens friction on the center wheel pinion. The watch comes from a small series of precision tourbillons that the Smith Co. destined for the Kew Observatory Contests between 1904 and 1909.