This is a cutaway of the Radiamic liquid-fuel thruster. It was also designed C-1, for Common Engine.
Starting in 1965, it was produced by the Reaction Motors Division of the Thiokol Chemical Corporation as a versatile, small liquid-fuel auxiliary rocket engine adaptable for a number of launch vehicles and spacecraft control systems. It could produce around 80-100 pounds of thrust.
This engine was donated to the Smithsonian in 1976 by NASA's Marshall Space Flight Center.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.