https://www.colophon-foundry.org/typefaces/perfin/

Perfins or ‘Perforated Initials’ first appeared on postage stamps in 1868. Companies perforated text and symbols into their stamps to protect them from theft. The use of perforations meant there was no need to overprint onto the stamp image. Perfin was created based on the letterforms seen on these stamps, and is a clear, versatile display typeface.