In regards to the terminology, best I can tell the 10’6” IH was added as an optional standard in 1941, and didn’t change again until 1947 when the 10’0” IH was removed from
What we often call ‘1944’ or ‘postwar’ cars simply have SREM Improved Dreadnaugh Ends, but the standard itself didn’t change. Those just happened to be the latest (trademarked) end they produced. The majority were 10’6” IH cars, but as we know, there were a fair number of 10’0” IH cars built too.
The “proper” terminology is something I’ve been trying to figure out, because some of it is modeler/railfan/historian terminology, rather than from the actual standards. It is helpful to a certain extent, but we are usually using visible components to describe the variants when I believe the standard was more about the dimensions and underframe is than the carbody. This means, for example, that we often omit cars with Pullman-Standard or ACF carbuilders ends from identification lists as if they weren’t AAR Standard cars of whichever type.
Technically, I think that a 10’0” IH car with an Improved Dreadnaught End is a 1937 AAR Standard Car, and one with a 10’6” IH is a Modified 1937 AAR Standard Car, if built before 1947 anyway. After that point it’s a 1947(?) AAR Standard Car.
I know that’s not the terminology we usually use, but what do the experts think?
Modeling the New Haven Railroad 1946-1954 | https//:blog.newbritainstation.com