The Seaboard Air Line Railroad (reporting mark SAL) existed from April 14, 1900 until July 1, 1967, when it merged with Atlantic Coast Line Railroad to form the Seaboard Coast Line Railroad. The B7 box car was nicknamed "Turtleback" due to the shape of the roof. It is a 40-foot, single-door box car that had an interior height of 10'-0". These were built by Pullman-Standard in 1941.