David:
I think we are both correct, if that is the right way to describe it.
I agree that the "vent windows" are possibly unique to non US production at least according to the photo records I have.
If we just talk about International Harvester vehicles, I have photos of same from not only the US and Commonwealth countries that show a lot of detail variations but also from such countries as Finland, Norway, Belgium etc. that have one heck of a lot of such minor variations. Particularly as regards the cabs and bodies. Assuming that a hell of a lot of chassis/cowl exports took place in the late 1930's, early 1940's, one could imagine any number of different possibilities as regards the cabs in particular and of course the various bodies as well.
Sadly, the AWM photo repository does not do a really great job of identifying the vehicles in their photos and uses fairly generic terms, often not even identifying the makers. It is left to us enthusiasts to try to sort out the end game ID.
Let's keep trying.........
Bill