A perfin (a contraction of 'PERForated INitials'), also called SPIFS
(a contraction of 'Stamps Perforated by Initials of Firms and
Society's'), is a pattern of tiny holes punched through a postage stamp.
Organizations used perforating machines to make perforations forming
letters or designs in postage stamps they purchased, often in bulk, with
the purpose of discouraging pilferage. The size and number of perfin
holes, and sometimes the design permitted, is usually regulated by law
or postal regulation in the relevant country.