A leading manufacturer of high-quality clocks, watches, and chronometers. Charles Frodsham was the last active member of a family that had played a prominent role in London clockmaking since the late eighteenth century. In 1840, he became a partner of John Roger Arnold (?-1843), who inherited his famous father's business. The Frodsham firm survived Charles's death in 1871, but gradually subcontracted its production. However, its quality standards remained among the highest in the trade. The firm is still in business. At the Great Exhibition of 1851 in London, he displayed a 3/4-plate watch, which he 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 all of its most important timepieces.