A series of 24 cards issued in Canada by the YORK Company of Canada. One was inserted into each package of their QUAKER MUFFETS CEREAL and YORK PEANUT BUTTER TWIST (apparently a very short lived product that combined Peanut butter and jam in the same jar). Although no guide that I know of lists them or provides an actual date of issue, the card does have a copyright date of 1969 on it. The design of the card is fairly unique. Each card is set up in a gate fold manner. With a picture of the subject on the front, which when folded open shows the interior structures of the subject or how they might look if one had x-ray vision. It also give a brief description of the subject on the upper inner part of the card. The back of the card has advertising for the products and a description of how one could send away for a wall plaque to display their card collection on. The Card measures 2 7/8 inches by 2 3/8 inches approximately when closed. When opened you can double those 4 13/16 inches by 2 7/8 inches approximately.