Mine was rivetted as are most I have seen in 1951. Be careful. Some states are very picky and will balk if they determine the serial number plate has been tampered with. A fellow member from NC tran into this with an overzealous dmv person.
Do a little more reserach and make sure your plate conforms.
Oh, and it's a serial number, not a VIN. VINs didn't come about until the 60s. The numbers on my plate actually indicated sequence of mfr (e.g. 6504th car made that month!) Letters showed month and plant location.
My seller actually provided a clean KS title which used the body number listed on the firewall. Some states back in the day actually used engine numbers (not much help if it was swapped out). My Vin verifier person here in CA didn't pick up on this and as long as the body # matched what was on my KS title, she was good with it, and the DMV accepted it.
Good luck.