The 2356 Southern F3 B unit was the final B unit introduced by Lionel during the postwar era. Of the three B units produced by Lionel -- the Santa Fe, New York Central and Southern -- the Southern is the most difficult to locate as well as the only only to have a number stamped on its body. When a 2356 B unit is coupled between a pair of AA Southern diesels, the end result is an impressive-looking ABA unit. The ABA lash-up was both prototypical and a common sight on US railroads during the 1950s and 1960s.