Photo shows actual production boxcar - each car will have sequential numbering utilizing 7146xxx numbering so you can run multiple AEC box cars in your train.
Argonne National Laboratory is a science and engineering research national laboratory operated by the University of Chicago Argonne LLC for the United States Department of Energy located in Lemont, Illinois, outside Chicago. It is the largest national laboratory by size and scope in the Midwest.
Argonne was initially formed to carry out Enrico Fermi's work on nuclear reactors as part of the Manhattan Project, and it was designated as the first national laboratory in the United States on July 1, 1946.
In the post-war era the lab focused primarily on non-weapon related nuclear physics, designing and building the first power-producing nuclear reactors, helping design the reactors used by the US's nuclear navy, and a wide variety of similar projects.
In 1994 the lab's nuclear mission ended, and today it maintains a broad portfolio in basic science research, energy storage and renewable energy, environmental sustainability, supercomputing, and national security.