in which coincidence of markings is sensed optically, e.g. peek-a-boo system

Full Title

Information retrieval from punched cards designed for manual use or handling by machine (G06K19/00 takes precedence; detection or correction of errors by rescanning patterns G06V10/98; checking correct operation of card-conveying mechanisms G06K13/06); Apparatus for handling such cards, e.g. marking or correcting > in which coincidence of markings is sensed optically, e.g. peek-a-boo system