Im curious to see what the answer to this is.
The line wouldn't use one off rivets and it's highly doubtful they'd run out so if it is factory there would be more like these around. They also wouldn't be installed like normal rivets so it's introducing a whole different process to install it.
The vin tag looks like it's scratched up around them like there was other ones there before but that could be from when it was removed before for the restoration.