What is "perfin"

n. 1 (context philately English) perforated initial; a series of small holes punched into a stamp and forming a letter, series of letters or other design for the purpose of preventing the unauthorized use of the stamps. 2 A stamp marked with perforated initials.

In philately, a perfin is a stamp that has had initials or a name perforated across it to discourage theft. The name is a contraction of perforated initials or perforated insignia. They are also sometimes called SPIFS (Stamps Perforated with Initials of Firms and Societies).