The Secret Purpose of Mail Defacement

Mail cancellations are not just for dating letters; they are deliberate acts of destruction. By physically defacing a stamp with ink, postal workers ensure the stamp cannot be stolen or reused.

The markings used to ruin stamps are technically called killers or obliterations. While we often call them postmarks, that term actually only describes the stamp showing the date and location. Some stamps are even pre-cancelled before they reach the public, meaning they are born destined for the trash. It is a fascinating example of how a simple mark protects a global commerce system.