Short answers, pulled from the story.
The Fort Bliss 100th Anniversary issue of 1948 was the first U.S. postage stamp to depict a space vehicle. Its central design shows a rocket modeled after the V-2, which classifies it as a space stamp in the field of philately. More than 64 million copies were issued.
The Project Mercury stamp of 1962 received more than three million First-Day of Issue cancellations. The average for other commemorative stamps at that time was around half a million, making the Mercury issue roughly six times more popular on its first day.
The stamp was printed before Colonel John Glenn's orbital flight had taken place, so the Bureau of Engraving and Printing kept its existence secret in case the mission failed or was canceled. Sealed packages marked Top Secret sat in post offices across the country, and postmasters were not allowed to open them until Glenn returned safely on the 20th of February 1962.
While orbiting the Moon on Christmas Eve, Commander Frank Borman, James Lovell, and William Anders each read a passage from the Biblical creation story, specifically verses 1 through 10 of the Book of Genesis. Leonard E. Buckley based the Apollo VIII stamp design on Anders's Earthrise photograph with the words "In the beginning God..." overlaid on the image.
Some copies of the First Man on the Moon issue are missing the red color, which caused the stripes of the flag emblem on Neil Armstrong's arm to be omitted entirely. That printing error made those copies scarce and significantly more expensive than the standard issue, of which more than 152 million were printed.
Robert T. McCall designed the greatest number of U.S. space commemorative stamps, including the Space Achievement Decade issue of 1971, the Skylab issue of 1974, the Pioneer issue of 1975, the Viking missions issue of 1978, and the Apollo-Soyuz issue of 1975. McCall was based in Paradise Valley, Arizona.