These four fins are attached to the bottom of the U.S. Army's Nike booster rocket, which launched civilian and military payloads, such as the Cajun sounding rocket and the Ajax missile. The booster produced fifty thousand pounds of thrust for three seconds. When used to launch the Cajun, the booster was modified and fitted with four fins instead of the standard three for military missiles.
The National Advisory Committee for Aeronautics donated an entire Nike-Cajun sounding rocket to the Smithsonian in 1958.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.