Hi Helen thank you for sending in the following cameo question:
"Hi, I have no idea why I bought this except that it looked old, beautiful and I never owned a cameo. Can you tell me by looking at it how old it is and what value it might have? The cameo is translucent when held to light and the stones are agate. Measures almost 2" across."
Yes, you are definitely onto something, fittings and findings on the reverse of a piece of jewelry often provide more clues than the front if they are the original. But with cameo jewelry the carving on the front will provide crucial dating clues. Because it is the actual cameo itself, we want to date, the mount may have been a later addition.
Looking at the back, it looks like a simple "C" clasp and this indicates the earliest type of catch although it is still sometimes used on new jewelry.
The material being agate is interesting because, Agate and hard-stones were used before shell. Shell was easily available and cheaper (because shells are found on the sea-shore) and so became popular.
All things being equal, hardstone cameos, like your agate cameo, will last longer than a cameo carved from shell, because agate is harder on the Moh's scale of hardness.
If possible, please upload a photo of the front of the cameo, it will help us with the date.