Cameo style Carved Seashell

This is a beautifully carved Cameo shell. It's signed by an artist and is very solid. I think it may be old but it still has a very good shine that can especially be seen in the pic of the artist signature. Any help would be appreciated. Some questions are. Who is the artist? When was it made? Where was it made? What kind of shell is it? Any idea as to the value on a piece like this.

Thanks,

Mike