Sorry for the delay posting you question. A list moderator has to okay only the first post from a subscriber. There is no way to change that but it would keep us from being overrun by a spammer.
I've attached one page from the May, 1973 roof hatch car assignment list. We can post whatever is in the archives files. The lists include both 40 and 50 ft cars and
show clay, bauxite and phosphate. I can add one more commodity I have seen in the files, aluminum dross from Ford. We need to confirm but those few cars were very early and I remember only had two roof hatches. Is anyone aware of other shippers or loads?
We have accumulated plenty of material for a TIES article on these cars if anyone would like to take that on as a project.
For modelers, the WrightTrack model builds into a very good looking car. I've attached a photo of one I did before it was completely decaled and weathered.