This is a mockup of the Gemini Adapter, which was attached to the aft end of the crew cabin. Below this was the retrograde section, with contained some components of the cooling system and the retrograde rockets. At the bottom (the larger end) was the equipment section,which housed major components of the electrical, propulsion, and cooling systems. The equipment section also contained the primary oxygen supply for the Environmental Control System. At the very bottom was the launch vehicle mating ring.
McDonnell Aircraft made the Adapter and McDonnell Douglas donated it to NASM in 1970.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.