I think all three are Walthers. My logic? The coupler cover on A is identical to the ones used on their mid 90s offerings for 89 foot cars. The cover on B looks like a modified version of it, with two more screws holding it on. And the black coupler spring in C is what's under the yellow cover in A.
I have a number of HO auto racks that I am not sure of the manufacturers. I wonder if anyone can help me identify them. They all have a different coupler mounting system. I am pretty sure that "C " is made by Walthers. Any help would be appreciated. Thanks in advance