78. Perfin varieties: Perforated initials, or perfins, are applied to stamps as a security measure to keep employees or unauthorized persons from using them. All are done locally and varieties include doubled, impressed from the back or front, pairs with one missing, and others. Values are greater among specialists.
Type 78: The perfins are missing on the bottom pair of this 1/2¢ Nathan Hale block (Scott 653).