American test pilot and astronaut (1921-1966) who was killed when his F-104 Starfighter chase plane collided with an XB-70 Valkyrie; Walker had been flying in a tight group formation for a publicity photo, and was knocked out of control by the supersonic bomber's wake. Commemorative cover bearing a cachet honoring Walker and the X-15, signed on the front in ballpoint, “Joe Walker 9/23/63.” In fine condition, with a couple small slips added to front of cover before signature. JSA/Scott Cornish Auction LOA and RRAuction COA.
