In philately (stamp collecting) 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.
In 1868 Great Britain became the first country to use perfins. The practice spread quickly to Belgium (1872); Denmark, France, Germany and Switzerland (1876); and Austria (1877); the U.S. finally allowed perfins in 1908.
In Britain, unused postage stamps could be redeemed for cash at the post office. By agreement with postal authorities, a perfin stamp on a letter could be used only by the owner of the perfin. Therefore, a stolen perforated stamp would be of no value to the unauthorized bearer, meaning that the use of perfins gave organizations better security over their postage. The demise of the perfin came about by the widespread use of postage meter machines which obviated the need for perfins.
As with any stamp – aiming to get the best condition copy you can is desirable – whether that is mint or used.
The Perfin Society – Great Britain based Perfin Society