Hi and welcome.

What a beautiful vase! French cameo is not my area, but I'm sure others will be able to help you more with the background information - that's what we do here.
However, we are not appraisers and we really do not tend to discuss values, which are subjective and can change rapidly with fashions in the secondary market. Something is worth what somebody is willing to pay for it, in that place, at that time.
Your best bet for obtaining a ball-park figure would be to study sold auctions of similar pieces.