Aperture cards are a popular microform for handling large originals such as maps and plans.
The concept of a single film image set into a “window” cut into a card carrier dates from around 1934 and was widely adopted for engineering drawing applications after the format was subsequently standardised by the US Department of Defence.
The dimensions of current aperture cards are 187.25 X 82.5mm because during the 1970’s Hollerith punched cards of that size were commonly used for data input to computer systems.
The mechanical sorters used for computer applications were adapted for sorting the aperture cards. It is still possible to punch the body of the card to record data such as the drawing number and original drawing size and to sort the cards mechanically on special card sorters.