Ed, Thanks for the description. Now I know which car we are dealing with. The Army had some out at Fort Bliss years ago and I was afforded plenty of opportunity to examine them closely.
Unfortunately there do not appear to be any of these 70-ton flat cars on the 48-49-50 Landmesser hot box list. Finding myself to be ever less of a purist as vision diminishes and hand tremors increase, I'll probably have to have a couple of these flats anyway.