A Star Trek convention in the 70s. Yes, that’s George Takei judging.
Dark Phoenix looking particularly sullen. WorldCon, 80s.
Orion slave girl with some nerd at a Star Trek con in the 70s.
More 70s Star Trek. Lots of Vulcans!
Red Sonja! This particular Sonja is Wendy Pini, who would go on to illustrate the classic ElfQuest.
Elric of Melnibone and his consort Cymoril. WorldCon, 70s.
Rollerball cosplayers, late 70s.
Ming the Merciless and Maleficent. WorldCon, 70s.
Comic book and movie characters weren’t the only cosplay subjects — here you can see a woman dressed as National Lampoon’s comic strip character “Danger Rangerette”. 70s.
Several Red Sonjas and a lucky wizard. WorldCon, 70s.
Lastly, a classic — Doctor Who, K-9, and Leela. WorldCon, 70s.
Source: fanboy