StampNews.com got interesting info: according to Postal Museum of Smithsonian Institution the stamp, released on September 9, 1969, was made from the same master die that the astronauts took with them to the moon. Additionally, it was the largest stamp the United States had issued up to that point.
In 1969 during the Apollo 11 moon flight, the astronauts took with them a die of a postage stamp which they pulled an impression of when they touched down on the moon. Thus, creating the moon's first postage stamp! Once the die was returned to earth it was used to produce the 10 cent airmail stamp issued in September of 1969.
The stamp's designer, Paul Calle, had previously designed the 1967 Accomplishments In Space stamp featuring NASA's Gemini Program. In addition to his work designing postage stamps, Calle was a professional sketch artist for NASA. He had sketched the astronauts as they prepared for their mission and also watched the Apollo 11 launch at Cape Kennedy.
His design for the Moon Landing Issue stamp illustrates an astronaut stepping out of the Lunar Module on to the surface of the Moon. In the three weeks following the announcement of the stamp's release, the Post Office Department received over 500,000 requests for first day cancelled covers of the stamp. One fifth of these requests came from overseas. The stamp issue became and remains a real hit in the world of philately.