English gold minute tourbillon with power reserve Circa 1905

Gold open faced lever with tourbillon and power reserve by Charles Frodsham
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A very fine and rare English 18 carat gold open faced one minute tourbillon keyless lever watch with power reserve, circa 1905. Gilt finished 3/4 plate movement, chain fusée, raised barrel engraved with Honour cyphers, stainless steel three armed Nielsen type 1 tourbillon carriage with double roller lever escapement. Gold cuvette engraved 1st Class Kew Obs. ‘Especially Good’ With The High Number of 90.8 Marks. Silvered matte dial with Roman numerals, blued steel spade hands, outer railway minute divisions, 24 hours power reserve and large sunk subsidiary seconds. Heavy plain case, stepped bezel and back. Case and cuvette signed with casemaker’s mark ‘RN’ for Robert North, dial and movement signed by maker and numbered, London date letter for 1905. Comes with Certificate of Origin and original Key Observatory Certificate.
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Diameter: 57 mm
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Signed: Chas. Frodsham AD FMSZ By appointment to the King 11 New Bond Street London No. 09133