Tessa, I'm not sure what you mean exactly by Porcelain Cameo. A cameo is described as a carving having the design in relief or raised above the background surface. Cameos are usually made in layered materials such as agate or shell to achieve contrasting colors.
You can find information about antique cameos HERE...
Maybe you mean "porcellana" - Porcelain derives its present name from old Italian porcellana (cowrie shell) because of its resemblance to the translucent surface of the shell.
I'm thinking you may have acquired an antique porcelain pendant? If so, is the porcelain image typical of Limoges, if so one would be inclined towards a French origin. Are the colors vibrant? Are there any hallmarking on the surround? Is it surround by pastes stones, for example? If so, are any of the stones flat or dead looking? Flat, lifeless stones will detract from the value. Tessa, the brute matter of how much is it worth is not just determined by one value.
