This is a Vanguard TV-2BU rocket, the U.S.'s first rocket specifically designed to launch satellites. As part of the Vanguard program, the Vanguard TV-2BU test vehicle was prepared for launch by the Martin Company on September 3, 1957. But due to a technical problem the mission was cancelled. The next launch opportunity was on June 22, 1959. However, the TV-4BU test version of the Vanguard was launched instead and orbited Vanguard 3.
Meanwhile, on March 17, 1958, the first successful Vanguard satellite was launched as Vanguard 1 atop a Vanguard TV-3BU rocket. The TV-2BU rocket was thus never used in the program but was essentially a duplicate of the Vanguard 1 vehicle and had the same markings. This TV-2BU was donated to the Smithsonian in 1958 by the Naval Research Lab.
Naval Research Laboratory