I would like to suggest that you abandon your plans to make tortoiseshell picks, and buy the excellent "Tortis" imitation tortoiseshell picks instead.

The fact that the tortoiseshell is antique is irrelevant, using a tortoiseshell pick makes a statement, and that statement is the same one you would make if you played a guitar with an ivory nut and saddle.

I don't have to spell it out, do I ?