VIN Rivets

Plymouth 65 said
My 65 Formula S Barracuda has the vin riveted on drivers side front door jam. I bought the car off the original owner. Removed the tag to restore the car. Rossett rivets were used originally. 65'

My 65 Dart GT has no rivets. Manufactured Dec 4th '64. Maybe later in the 65 model year they were added?