An onyx and diamond fob seal, late 18th/early 19th century, carved as a seated spaniel in black

An onyx and diamond fob seal, late 18th/early 19th century, carved as a seated spaniel in black onyx, its eyes and collar set with cushion-shaped diamonds, the base set with a banded onyx intaglio carved with a laureated man in profile, possibly Julius Caesar, suspended from a gold split ring, total length including split ring 4.4cm, intaglio 1.5 x 1.2cm, dog with one paw deficient