This is the left boot from the Gemini G3-C spacesuit that was made for and worn by astronaut Walter "Wally" Schirra, Commander of the Gemini VI mission in December 1965.
The G3-C suit was only made in the Intra-Vehicular configuration, and consisted of five major componenets: the main torso, helmet, boots, gloves and neck seal. Additionally, Schirra wore a constant wear garment and life vest assembly. The suit permitted freedom of movement, and was equipped with communication and bio-medical transmission equipment.
NASA transferred this suit and its components to the Museum in 1968.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.