Hmmm...looks very much like they bought it from the Erie/EL. Well, that saves me money. Thank you!
As for the offset door, I didn't know these had them. The B&O Canstock cars, yes, and some FGE cars I saw years ago, but not plain RBLs. But a closer look at my MILW pictures show that their 2800s, at least, DO have offset doors. So the old Walthers tooling wouldn't be correct after all, at least for the series Atlas is making.