According to The Frodshams - The Story of a Family of Chronometer Makers by Vaudrey Mercer, p. 255, Appendix X, the present movement was manufactured in 1881 by Nicole & Co.
Charles Frodsham (1810-1871) was a leading manufacturer of high-quality clocks, watches and chronometers and the last active member of a family that had played a prominent role in London clockmaking since the late 18th century. In 1840, he became a partner of John Roger Arnold who inherited his famous father's business.
At the Great Exhibition of 1851 in London, Frodsham exhibited a three quarter plate caliber signed with the letters "AD. FMSZ", a cryptogram for the year 1850. The code is formed by the numerical sequence of the letters in "Frodsham," with a "Z" for zero. The firm subsequently used the code for its most important timepieces.
During this period Frodsham was also closely connected with Nicole Nielsen who produced the majority of the movements, including some of the most accurate and perfect tourbillons ever made.
After Charles' death in 1871, the firm continued but gradually subcontracted its production. However, its quality standards remained among the highest in the trade.
For a note on Nicole Nielsen see lot 228 in this auction.