Sought-after complete set of 20 international stamp sheets signed between 1968 and 1971 for German stamp dealer Hermann E. Sieger. The collection consists of commemorative postage stamps from around the world, each signed in various ink types by an Apollo or Mercury-era astronaut, including: Neil Armstrong (Belgium), Stuart Roosa (Hungary), Richard Gordon (Hungary), Gene Cernan (United Arab Emirates), Rusty Schweickart (Yemen), Edgar Mitchell (Romania), Alan Bean (Romania), James Lovell (Romania), Scott Carpenter (Paraguay), Frank Borman (United Arab Emirates), Wally Schirra (Paraguay), Don Eisele (Yemen), Gordon Cooper (Paraguay), John Glenn (United Arab Emirates), Walt Cunningham (United Arab Emirates), Jack Swigert (Romania), Tom Stafford (Yemen), Jim McDivitt (Yemen), Charles Conrad (United Arab Emirates), and Dave Scott (United Arab Emirates). In overall fine condition. Accompanied by a full letter of authenticity from Zarelli Space Authentication for the Conrad signed stamp, and by 11 of the original German-language biography cards.