George, that's great. I see by your post on the other thread that you were able to get the GN for a reasonable price. It also sounds like the apparent large rust spot on one side wasn't - that's even better.
With regards to the tank car there are two variations which have to do with the way the handrails are attached.
There is the 5 stanchion version
and the three stanchion version
...and there are a couple of odd balls that are out there.
This one has a complete overprint of black litho which covers up all of the script American Flyer label. If you look at the car in reflected sunlight it looks like the litho for the "American Flyer Tank Line" part did not print correctly - that is there are pics in the litho surface. I've only seen this single car but there have to be more out there - no one would just run an overprint for a single car
The second one has to be a tool test car - it is the old lithography but it has holes punched for ladders/platforms and nameplates which were part of the enameled tank cars which were manufactured later. It is easy to see this car never had these things attached. I've seen one other car like this but, again, there have to be more out there.