Cameo: Costume Jewelry?

I actually think this is just costume jewerly, and I bought it with the idea that I will cut up the pin in the back and turn it into a clustered metal necklace. But, before I do so, I would like to make sure that it is costume jewerly I'm cutting into. The picture is a little discolored. It's a cream color in some parts, and in other areas, it has an almost orange tint to it. I assume those are stains and am hoping to find a way to clean it off, but I'll wait to do that. The cream colored picture is set on a rose background. The picture actually has a lot of detail to it, and it's REALLY pretty, which is why I had no problem paying $10 for it. Other than the color, I can't really see any flaws in the picture, but the rose colored background it's set on as a million flaws. It does have characteristics of a smoothed rock, actually, because some parts look shiny and others look dull, but the back of it is smoothe like a shell with the exception of the indention in the center where the picture is. Also, some parts of the rose colored background looks a little beaten up, although I'm not sure how the picture didn't get affected. The background has almost indentations in it, but again, it's all smoothed out. It is placed in what looks like a very small picture frame with very small, shiny stones around it, which almost looks like beads or something.

If I had to guess, from a novice perspective, I would assume I have an early or mid 1900s cameo costume jewerly that has a greece woman picture placed on shell.