A photo of one of these boxcars as GM&O 20188 surfaced on the 'bay. One of Ted Culotta's auctions.
At first I thought it was some kind of War Emergency boxcar but the Howe truss is wrong (and it has less panels) and the 4/5 end, hence 10' IH, also made it unlikely.
Tim O'Connor commented previously on the pre-war origin of these, as ex GM&N.
I'm wondering if anyone knows more about them. In particular, what type of roof they had, and whether any other roads rostered anything similar?