Externally, the FA-1 / FB-1 could be distinguished from the FA-2 / FB-2 ( FPA-2 / FPB-2 ) by the position of the radiator shutters the FA-1 / FB-1's shutters were at the far end of the carbody, whereas on the FA-2 / FB-2 they were further forward, the design having been modified to allow the installation of a steam generator behind the radiator.
