This is a partial cutaway of a U.S. solid-fuel 4.5 inch (11.5 cm) unguided air-to-ground rocket of World War II. It was an outgrowth of the M-8 4.5 inch aircraft rocket, which was originally developed as collaboration of the National Defense Research Committee, Army Ordnance, and Naval Ordnance, at the Navy facility at Indian Head, Maryland in 1941. The 4.5 inch rocket was extensively used by Navy and Army Air Forces units in both Europe and the Pacific.
This version of the missile was modified or manufactured at the Naval Ordnance Test Station (NOTS) in California. Originally, the missile had four fixed fins but this version has folding fins. It was found in Smithsonian collections but was likely transferred by the U.S. Navy.