When the Smithsonian received this artifact from NASA in 1967, it was the structural framework of a Mercury capsule only, without inner or outer skin or a forward recovery section. NASA had used it for instrumentation and wiring tests. The Michigan Space Center later converted the framework into a mockup of a Mercury capsule mounted atop a Redstone booster. It is no longer displayed outside on the booster.
Project Mercury was the United States' first human spaceflight program, with a goal of launching a series of one-man capsules into space. Six astronauts flew in Mercury capsules from 1961-63, the first two were lofted into suborbital trajectories by the Redstone rocket, the last four into orbit by the Atlas ICBM.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.