Port-a-punch Perforations

From 1958 onwards some manufacturers could print punch cards with pre-perforated columns for use with the IBM Port-a-Punch or IBM 3000 Information Recorder I. These allowed a user to punch a card without a punch machine, rather using a stylus to punch the perforated chads out of the card using the special tablet to hold the card. Port-a-punch perforated cards were limited to 40 usable columns as only every second column was perforated.