In 1966, Stan Lee had Captain America and Spider-Man costumes made for the marketing department. A "lucky" Marvel staffer would be given the honor of dressing up for a news interview, magazine article or photo-op. One of the last times these were used was at the 1976 Marvel Comics convention. They were so well-received by fans at the conventions that letters arrive inquiring if they could be rented for private events.
If you have ever come across a 1970's comic book or piece of merchandise that was signed with just a Super Hero's name it was from one of the hundreds of actors hired by Marvel.