This is a U.S. Navy Poseidon C-3 submarine-launched ballistic missile (SLBM), deployed from 1971 to the early 1990s. Developed by Lockheed as a successor to the first-generation Polaris SLBM, Poseidon C-3s were two-stage, solid-fuel missiles with a range of approximately 5,300 km (3,300 miles). Sixteen missiles were carried on an individual ballistic missile submarine, with each missile having up to 14 independently targetable nuclear warheads. This Poseidon C-3 was assembled from spare parts by Lockheed and donated by the U.S. Navy to NASM in 1973.
This object is on display in Rockets & Missiles at the Steven F. Udvar-Hazy Center in Chantilly, VA.