It is difficult to tell from a scan but it looks like "French" ivory, which is celluloid with the grain printed on, to appear to be ivory. The best way to tell the difference is to heat a needle red hot & try to pierce the edge. If the needle goes in it is celluloid. The needle will not pierce ivory, which is much harder, as is bone. Bone is fairly easy to tell as it had small dark lines (most 2-4 mm long, running in the same direction) throughout the surface.