Two 8-cent stamps commemorating a decade of space achievements were placed on sale August 2, 1971, at Kennedy Space Center, Florida, and Houston, Texas. They were placed on sale at two post offices rather than the usual one because of extraordinary interest in the stamps at the time of issuance.
The stamp designer was Robert T. McCall of Paradise Valley, Arizona. They were issued in sheets of 50, with an initial printing of 150 million.
Reference: Postal Bulletin (July 1, 1971).