Do not store in plastic bags,hot places or on cotton pads in boxes-all this drys them out. The best place is just sitting in a drawer in jewelry box,etc. They are brittle is you drop them on floor they may break. Also they can be worn down. You see many rings with no features left on face because the person has rubbed them.
Pin backs are a good clue.
Also, white gold was not used until after 1910. Greco Roman noses were predominate from 1910 back. Today most new cameos have pug noses, sweeping hair, slim bodies like Barbie. Most all cameos for sale in the US today are apprentice carved. There are many fine Master carved cameos being carved today in Italy-most go to Japan.