Desirable group of six blocks of four 4¢ Project Mercury postage stamps, each signed in ink by one of NASA's original astronauts. Includes: Gus Grissom ("Virgil I. Grissom"), John Glenn ("J. H. Glenn, Jr."), Alan Shepard ("A. B. Shepard, Jr."), Wally Schirra ("Walter M. Schirra, Jr."), Gordon Cooper ("Leroy Cooper, Jr."), and Deke Slayton ("Donald K. Slayton"). In overall fine condition, with poor-to-moderate signature contrast.
