Signed Netsuke

Hello there, I'm wondering if anyone can tell me how much this Netsuke is worth. The netsuke can roll it's face around to a friendly face or an angry face. I think it might be made out of ivory. My mother got it from her mother who bought it out of an antique shop.

Here are some pics-
http://s1177.photobucket.com/albums/x356/CocoKakao/Netsuke/

Thanks so much!