English gold 7½ minute flying tourbillon chronograph Circa 1917

Gold split second full hunter chronograph by Charles Frodsham
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An English gold hunting cased keyless lever 7½ minute flying tourbillon watch with split seconds chronograph and 60 minute register, circa 1917. Case hallmarked 1904. The watch features a gilded frosted 2/3 plate movement with a lever escapement mounted to the tourbillon carriage, which completes one revolution every 7½ minutes. It has a freesprung bimetallic compensation balance, a blued steel spring with an overcoil, a diamond endstone, and steel chronograph work partially visible through the backplate and a split mechanism beneath the dial. It is signed Cha. Frodsham by Appointment to the King, 27 South Molton Street, London, AD.Fmsz, and engraved with gold medals of honour. The offwhite Willis type enamel dial, signed Charles Frodsham 09765, AD.Fmsz., displays Roman numerals, an outer chronograph track with Arabic numerals, two sunken subsidiary dials for constant seconds and a 60 minute register, blued steel spade hands and gold and blued steel hands for the chronograph.
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The case is made of 18 carat gold with a plain polished finish, complemented by a plain polished cuvette and pushers for the chronograph and split function at the band. It also features a gold pendant and bow, a pusher for the handset with protective shoulders, hallmarked London 1904, and the front and back covers are numbered. All covers are stamped with RN for Robert Benson North within a rectangular cameo, and the pendant bears the maker’s mark A.B.
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Diameter: 55 mm
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Signed: Charles Frodsham, London
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The movement is operational, but the start and stop button for the chronograph is not functioning; however, the split button effectively separates and rejoins the chronograph hands. The hour and minute hands are adjusting smoothly. The dial appears to be in good condition. The case shows signs of light polishing, along with some minor marks and scuffs.
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This is the only known example of a split seconds chronograph watch by Frodsham featuring a 7 1/2 minute flying tourbillon carriage. Interestingly, the case dates to 1904, yet the address engraved on the backplate is one that Charles Frodsham & Co. moved to in 1915. Additionally, the movement’s serial number suggests a completion date around 1917. This date disparity indicates that the case was reused by Frodsham; such reuse of a high quality case is not unheard of—another case and movement discrepancy is known for a further Frodsham with a similar serial date to the present piece. As the Frodsham workbooks from this particular period are lacking and no Kew examination was originally undertaken for this watch, it is not possible to shed further light on its early history.