Commemorative cover with a cachet honoring the International Astronautical Congress held in Madrid, Spain, in October 1966, signed in ink by Frederica of Hanover, the former Queen of Greece; her daughter Sofia, the later Queen of Spain; Leonid Sedov, chairman of the USSR Space Exploration program; William Hayward Pickering, the father of Explorer 1; NASA MSC director Robert Gilruth; and Apollo 12 moonwalker Charles Conrad. In fine condition. Consignor notes that the cover originates from the collection of Josip Kotnik, a Croatian electrical engineer and astronautics expert who published the book Čovjek u svemiru [Man in Space] in 1968. The cover bears 1968 Kennedy Space Center postmarks on the front and back, commemorating Kotnik's visit to the facility.
