That Beretta finish can be filled and sanded, then a final coat over the top with any oil type finish. Done it with Tru-Oil. The problem then is matching the sheen, or shine of the rest of the stock. Being a separated piece, close would still be better than if it was just a portion of the stock itself. Just a matter of either polishing or scuffing to match. If you want a perfect match, do the whole stock with the same treatment.