I Believe that I have the same car as the C&O. The sides have metal dowels that that connect them and then the underframe is screwed to the sides.
It is not Mi-Loco or Mi-I-Scale. I also have a tank car.
Are the truck bolsters round and pressed onto the side frames on your car.
I got these cars in the Fall and have researched 17/64" and Q scale but cannot identify the maker.
Harold