I think it's more like if the player portrayed on the baseball card sold a certificate saying it's actually him on the baseball card with his signature on the c

I think it's more like if the player portrayed on the baseball card sold a certificate saying it's actually him on the baseball card with his signature on the certificate. The actual original of the card isn't traded. As the buyer, you don't end up owning anything new, you get just a signature from some guy.