This is a cutaway of the 100-pound thrust Radiamic liquid fuel rocket engine, also designated the C-1, or "Common Engine." The C-1 was developed from 1965 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, including the Saturn S-IVB or third stage and the Apollo Command and Service Modules. However, it never became operational. This object was donated to the Smithsonian in 1980 by the NASA Lewis Research Center.
NASA, Lewis Research Center