I'll take a shot at this question:
Bolster shape
Handle shape
and to a lesser extent - blade shape
If you Google Copperhead knives (or something similar) and look at what Case, Boker, etc. offer, you'll note a similarity in the front bolster as well as overall handle shape.
Plus, Copperheads are usually single bladed, but not exclusively so...
Hope that helps and maybe someone else who is more of an expert can chime in here...
Cheers,
Mike