Mermaid Riding a Fish Brooch

Recent acquisition for me. I have always loved mermaids (I think it's due to Diver Dan TV show I watched as a child...) Don't know much about this brooch. I found it on the internet and it looks like a Cyvra brooch but I can't find that mark on it. It does say "Oleg Cassini" which I recognize as a fashion designer, but that's all I know. Any information would be most appreciated (as always!) Thank you.