Gatwood, Elden J SAD
And more, note how different cars of the same RR and class looked. The end result in that your cars should look different. Especially hoppers and gondolas.
That bluish cast in that H21A is real. I remember that very well from my years crawling around inside these cars. It is not just the last load they carried, it was the abrasion down to bare steel.
We could engage in endless speculation, but this is the proof.