Trev gives the best advice in his last response. However, I read about a guy that made 3 or 4 repo Clovis points, took them to a reputable authenticator, and he passed them. The creator told him after the fact that he made them weeks earlier. You really can't tell. Certain lithic would be harder to repro. I would guess, so look on the net for lithic for sale. Stay away from pieces made of those lithic types. What I'd do If I were in the market end of this hobby. Treasure hunter makes a valid statement as well. However, at a local Flea market, a guy sells artifacts here. He supposedly is certified to authenticate as well. I go in and look at his inventory, but never buy. I'm just too skeptical. He has some pretty stuff.