This is a connector to a propellant line on the regeneratively-cooled liquid fuel rocket motor designed and built by James H. Wyld of the American Rocket Society (ARS) in 1937.
One major problem faced by early rocket experimenters was overheating of their small motors. Wyld's solution was regenerative cooling. In this system, the propellant circulates around the motor in a cooling jacket before injection into the combustion chamber where it is ignited with the oxidizer (liquid oxygen). The pre-heated fuel also aids its combustion. The motor was successfuly tested in 1938 and 1941.
Reaction Motors Division of Thiokol Chemical Corp. donated this object as part of the motor to the Smithsonian in 1952.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.