The Lionel Lines Berkshire Type 2-8-4-Locomotive No. 736 replaced the No. 726 in 1950 and would continue to be available until 1968. This was the longest production of any Lionel locomotive during the Post War period. This locomotive came with Magnetraction which was the most significant alteration from the previously issued No. 726. Also gone were the Baldwin disc zinc rimmed driving wheels. There were a number of other distinct changes that occurred over the production period of this locomotive. These are listed below:

1. Early issues (1950-51), would have just three windows in the cab. This is believed to be because Lionel wanted to distinguish this engine from the 726. For 1952, Lionel reissued the 726RR and for this model, and those 736's that followed, Lionel would revert to the four windowed cab.

2. Those engines built in 1950 and 1951 have large rubber-stamped number on the cab. All other issues, with the exception of some late post war period releases, would have smaller heat stamped numbers.

3. The trailing truck of this locomotive changed in 1954. Prior to this date, this truck was of die-cast metal construction, but those engines produced after 1954 would have sheet metal trucks with plastic side frames.

4. In 1957, Lionel changed the center rail pick-up assembly to a shorter, smaller roller assembly that was held in place by one screw.

5. Flagstaffs appear on the pilot in early issues. The earliest issued had hexagonal bases, while later issues had round bases and were sometimes painted BLACK. These extra detail parts would be eliminated after 1956.

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.