A perfin is a stamp that has a name or initials perforated into it.
The word “perfin” is short for “perforated initials” or “perforated insignia”.
Perfins are used to prevent theft and control how the stamp is used for mail.
How are perfins created?
Individuals, organizations, or government agencies add perfins to stamps after the production process.
The holes are punched into the stamp’s design to create a pattern.
Source: Google Search Labs/ AI Overview

The U.S. stamp bottom left is also pre-cancelled. Pre-cancelled stamps were used for mass-mailings, making it unnecessary for the post office to cancel them, and expediting their processing.
1961 First Definitive Issue (New Design), South Africa
Issued Jan. 20, 1969
Perf. 13½x14 |Phosphor frame |Wmk. RSA tête-bêche
SACC282 |1c |Rose-red & sepia |Coral Tree Flowers (Erythina lysistemon)
Perfin initials “D.C.”
1982 Fourth Definitive Issue (Architecture), South Africa
Issued Jul. 15, 1982
Perf. 14 |Design: A.H. Barrett |Engraving: Arthur Howard Barrett |Litho. |Phosphorized paper |No Wmk
SACC524 |10c |Carmine brown |Pietermaritzburg Town Hall
Perfin insignia “C C C” (or possibly “V V V”)
1923 United States of America (U.S. Presidents and prominent Americans)
Issued Jan. 15, 1923
Perf. 11×10½ |No Wmk
Scott 562 A165|10c |Orange |James Monroe (5th U.S. President)
Perfin insignia “WFH”
Pre-cancelled “Chicago IL”
[Sources: stampworld, South African Colour Catalogue 2023-25, Scott 2003 Standard Postage Stamp Catalogue Vol. 1]