Thank you for making your question to JustAnswer. My name is*****'m an Antiques Expert and I will try to help you with your particular inquiry. Please, don't hesitate to contact me any time or to make follow up questions if needed.
Could you provide a picture of the brooch?
Could you tell me if it has some kind of manufacturer mark?
You have a brooch made by Mikimoto, the King of Pearls. Mikimoto devoted his life’s work to cultivating perfect cultured pearls. The brooch is hallmarked for Mikimoto, and also carries the hallmark for 950 Silver, a higher standard than the US 925 standard.
Regarding the value of your item, I have just perform a market research of similar sold items as yours. I performed the research based upon the most recent finished auctions and private sells, so the value given is the real market value of your item. This is the only way to know the exact value of your unit.
The value will be in the range of 200-300$.
Please, use the stars to rate my answer or let me know if I can help you any further!