1926-29 Exhibit Postcard Back Jimmie Foxx. Graded POOR 1 (MK) by PSA. This issue marked Foxx's first appearance on a card and is considered his true rookie card. Interestingly, the 1926-1929 Exhibit Postcard Backs were not issued by the more established Exhibit Supply Company, but by an unknown company looking to share in the profits generated by the one-cent vending-machine cards. The copycat nature of the 1926-1929 Exhibit Postcard Back cards was obvious from the start, which most likely led to the company's legal department adding the text "Not To Be Used In Exhibit Machines" on the reverse. The offered card displays light horizontal creases through the center and bears a pencil notation on the reverse that reads "W461C."