This is a ground transporter for the Mark 4 reentry vehicle (RV). These RVs were used on U.S. Air Force Titan I and Atlas E/F intercontinental ballistic missiles that were deployed in the early 1960s, and they carried a W-38 nuclear warhead with a yield of about 3.75 megatons. Ground transporters were used to securely move the Mark 4 RVs, and with the missile in a horizontal position they were used to mate them to the missile. Both the manufacturer and donor are unknown.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.