Most cameos produced in the 18th and 19th centuries were mostly brooches, and most of the 19th & 20th century cameos are carved from shell. Your heirloom oval cameo brooch can also be worn as a pendant! If you wear it as a brooch it might be a good idea to have a jeweller attach a safety chain.
Have you tested the metal frame? If the frame is made from 9 ct gold it will most likely be a Victorian piece. Frames can be highly decorative or simple, some frames are made from rolled gold. Some frames are not made of gold at all, but from mixed metals. While at the other end, some high quality cameo frames are made from 22 carat gold and 18 carat gold.
As a price guide antique cameo 1875 set with two shell cameos of roman centurions on a bar engraved with scrip initials, marked 'Alb/18.C', in 18 carat yellow gold was sold in NSW in Australia in 2012 for $1098 AUD
Cameos that are created by a mould rather than carving are considered faux or fake cameos, although they are collectible in their own right as costume jewellery.
