PSA VS PSA/DNA Registry Question
Are cards that are PSA/DNA certified (red flip) not allowed to be added to PSA registry sets?
For example, I have a PSA graded 1984 Topps Tiffany Mattingly and I can add it to any set that it is eligible for.
However, I also have a red flip PSA/DNA certified 84 Topps Tiffany, that it won't allow me to add.
What's the deal?