Turns out they are from a Hoffmann's reefer, likely from the same car as the trucks. Nearly complete kits for these cars may be seen in this article. If you click over you will see that one of the kits lacks a frame, so I will strip the extra frame and put it with that kit. These cars are really uncommon, available 1938-39.
Then we get to my remnant car. Being so rare it will get a “project box” and will be rebuilt. I wish I had a spare set of Hoffmann's sides to make it really correct. It may emerge with Scale-Rail or Champion sides.
A final note on the trucks, they actually track OK (better than the truck in this article) but I think the wheelsets are likely replacements. In any case, an interesting group of parts I was happy to spot.