These are the major differences that define the five variations:
Variation A: SILVER rubber-stamped cab numbers, three cab windows, flagstaffs and a die-cast trailing truck (1950-1951).
Variation B: WHITE heat-stamped cab numbers, four cab windows, flagstaffs and a die-cast trailing truck (1953-1954).
Variation C: identical to Variation B except with a sheet metal trailing truck. (1955-1956).
Variation D: WHITE heat-stamped numbers, no flagstaffs, and revised center rail electrical pick-up assembly (1957-1968).
Variation E: same as Variation D except WHITE rubber-stamped cab numbers.
This locomotive was issued with three different tenders that were used over the time of production: 2671WX, 2046W, or 736W. All of the Berkshires that Lionel produced were designed to run on the standard O Gauge tubular track of the post war years and will not operate properly on the tighter curves of O27 Gauge track.