Atlas has three (four) different models:
Trainman "50' boxcar" (ACF 5300 cuft plate C)
Master "ACF precision design" (ACF 5095 cuft plate B)
Master FMC 5077 (early and late versions) plate B
In HO they've also announced a plate C FMC 5347 cuft car, not sure if that's coming for N too or not.
The "precision design" car is an early 1970s design with terminating ends, this type was never fostered by RailBox, but plenty of Class Is from that period.