This leg restraint was flown in the Gemini XII spacecraft, piloted by James Lovell and Edwin "Buzz" Aldrin. It would have been used to strap one of their legs to the ejection seat during launch and landing.
Gemini XII was launched on November 11, 1966, for a 4-day, 59-orbit mission. Highlights included 3 extra-vehicular activities (EVAs) by Aldrin, 5 hours 30 minutes total. Aldrin made extensive use of handholds and footholds to prevent unwanted movement during his tasks, and his techniques were an important milestone toward effective astronaut use of EVA. NASA transferred the Gemini XII spacecraft to the Smithsonian in 1968.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.