My mistake. I saw "StuGIIIA and 'B" and read "StuG IIIG" then couldn't find anything wrong with the "G"s
This addition goes back years. I went back to a copy of DOS vers 5.6 from 2002 and it was there as well and I'm betting it goes back further than that.
There is a "StuG IIIa" and a "StuG IIIb" because, in reality, there were "StuG IIIa"s and "StuG IIIb"s and for all game purposes they ARE identical . This is, I am nearly 100% sure, the result of someone in the past wanting to add more "realism" for "completness" to the OOB.
Don