I hate to break this to you, but it is not as old as you think. Looking at the clasp, I can tell that is is more modern than the 1800's.
However, I did Google the name Gragonard, and found a very similar item on E-Bay.
LOVELY VINTAGE PORCELAIN TRANSFER GRAGONARD CAMEO PIN - eBay (item 220418175982 end time May-26-09 14:57:08 PDT)
I would try to find a jewelry dealer in your area, that might be able to appraise it better than what the seller is asking for on theirs. I think yours is worth more, in my opinion only, because it is more ornate. I think it's very pretty, and because it is unique to jewelry of today, it might be worth something if you decide to sell it.