Athearn's plastic 50-foot Double Door Auto Box Car arrives in 1959 with the release of the 4-Bay Offset Side Hopper, and the open and closed versions of the Pickle Car. Athearn issued a similar tooling car in its metal line that dates to the late 1940s. The 1959 group of plastic model offerings carry 1230 series numbering. The first group includes: Burlington (1234), Great Northern (1235), Northern Pacific (1236), Santa Fe (1237), Pennsylvania (1238), and Southern Pacific (1239). Replacing the leading 1 with a 2, denotes a fully assembled example from the 1959 offering. The numbering changes in the early 1960s to the 1300 series numbers. Athearn appears to introduce four new road names in 1965: Southern (1318), Union Pacific (1319), Frisco (1320), and Louisville & Nashville (1321). Athearn discontinues offering fully assembled RTR examples about the same time as the 1965 additions, therefore kit versions are the only option for these offerings at the time.

The 1972 introduction of "Steam Era" rolling stock to Athearn's line utilizes the 50-foot Double Door Box Car tooling to become the Steam Era 50-foot Double Door Box. This new collection of kits is found in the 5030 series numbering.