Actually I believe both the MTL and Atlas 89' flats are 1973-79 era built ASH20 class units - however it is likely the only design change amongst classes were the jacking pads. Having said that, I haven't done I side by side for the two models yet. If I wasn't trying to finish off my Masters thesis I'd write something up for Model:160.
You're probably right. I know the MTL TTAX cars are in the number series for the Ash10a and Atlas did their O scale 89' in Ash10a stenciling as well so I went with that. Jason
