It would be impossible to tell you its value unless I could hold it in my hands and look at it; however, it appears to be from the photograph that you have a two-layer celluloid comb, which are generally from the Art Nouveau period (there is currently two of these in the LongLocks HairSticks Boutique on the Victorian Hair Combs page (http://www.longlocks.com/vintage-hair-combs.htm).  I also notice that it appears that stones are missing, which can significantly decrease its value unless you can find vintage stones of the exact color and size to replace the lost ones (no small task, it looks like a rarer olivine green to me).  Most importantly would be any signs of celluloid disintegration, or what is often referred to as "virus" (virus starts out looking like small dry, scaly patches)  If any virus is present, there's nothing you can do to stop what will be the eventual breakdown of all the celluloid in the comb.  The common belief is that virus is caused by keeping celluloid locked up where air can't get at it, so if your comb is in good shape be sure to display where everyone can see it and it gets plenty of air circulation!