An identical cameo of Hercules by Giuseppe Girometti (1780-1850) can be found in the British Museum, collection no. 1996,0608.1. The design is a copy of a Roman Imperial-period intaglio signed Gnaios from the Strozzi collection, also in the British Museum, collection no. 1913,0307.83.
Cf.: C. Gere & J. Rudoe, Jewellery in the Age of Queen Victoria: A Mirror to the World, London, British Museum, 2010, fig. 469, p.469, for more information.