This se-tenant block of four stamps was issued in conjunction with the 20th Universal Postal Congress. The stamps gave postal patrons a glimpse at several potential mail delivery methods of the future. These Space Age designs include a hypersonic airliner soaring through space, a mail delivery hovercraft riding along on a cushion of air, a shuttle involved in a mid-space mail transfer, and a land rover craft delivering mail to a space colony. Although these vehicles don’t actually exist, they are based on the industry’s estimation of what future mail delivery transportation could look like.