This is probably a pump part made by the American rocket experimenter Robert H. Goddard (1882-1945) about 1924. These pump experiments were carried out before Goddard had flown any rockets. His early pumps operated by the evaporation of liquid oxygen, although he had not yet fully developed his liquid-propellant motors using liquid oxygen and gasoline. However, as he recorded in his notes, these early "experiments with small pumps clearly demonstrated that a very small piston pump for liquid oxygen is very impracticable. The larger pump operated satisfactorily…." But following this period, Goddard switched course and designed and built a rocket without any pumps at all. He used a very simple but practical pressure-fed propellant feed system, also using, in part, the evaporation of liquid oxygen.
In 1959, Goddard’s widow gave this pump part to the Smithsonian as part of a large collection of artifacts.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.