Perfin banknotes and stamps (Perforated Initials/Insignia) attract collectors. Perfins were security features. A stamp with a perfin could only be used by the person/Company who owned the perfin. In the days before security threads, perfins were security measures. Perfins on banknotes had the same intention, to be used by a person, or more likely, a Firm which wanted to ensure cash would not be stolen or misused.  The note could be traced. These banknotes with perfins are rare and are very collectible. No charge for UK postage.