Something wonderful, that's for sure! There was a post way back about one like this - as I recall the conclusion was some kind of bone or mamouth (sp?) ivory. Now if I could just figure out how to cast that pattern........! Could you post some more pictures from other angles?
Ivory would show the lines (Schreger lines) in a certain angle to each other, I believe something at about 110-120 degrees, but not parallel. These lines are used to determine if it is Elephant ivory or Mammoth ivory, this one has a smaller angle.
>120 degs for Elephant,< 90degs for mammoth, but there are no schreger lines on that piece,It's Narwhal Ivory if Ivory at all.
Shine a UV lgt on it in a dark room, if it fluoreses,it's Ivory.
My thought would be that it is celluloid as well. You could do the hot needle test maybe on the bottom in one of the seam lines. Regardless of what the material is, it sure is a great looking handle. Nice find.