IVORY or What kind

[ladyDANAG]

I thought from the time I bought it that it was an ivory, I tried selling it on ebay and somone contacted me that this is rather a rare kind of clamshell. He refers me this link for further proof of what he said. Can anyone tell me what kind of clamshell it is and if it's not really an ivory handle? thank you and your reply is highly appreciated.