These are two Universal Clamping Devices (UCDs) flown on the Gemini XII mission. This mission, the last in the Gemini program, carried James Lovell, Jr. and Edwin Aldrin, Jr. into space in November 1966. Made of chrome-covered steel, UCDs were used by the astronauts to secure the tops of pouches and to perform similar tasks. Their manufacturer is unknown. NASA transferred them to NASM in 1968.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.