I engraved the polymer, you cant do a metal plate then attach it because its not part of the receiver since it could be removed and without being molded in there's no.way to make it permanent. Each class3 item (sbr, sbs, suppressor, destructive device) requires its on stamp and that wonderful $200 to be paid for each one. Honestly I think its worth it, if people can spend all that money on needless NcStar junk when they could have way cooler toys but that's just my opinion.