Why were stamps perforated ?
For many years, postage stamps could be used for payment of small bills and could be cashed on presenting them at a Post Office. This naturally led to the risk of the stamps being stolen. However, the Post Office would not accept stamps that had been perforated, thus reducing their value if stolen. In addition, unlike previous security methods such as underprinting, the original owner of the stamp could still be identified even if the stamp were used as postage.