[Phlogiston]

That is very true. Even larger manufactures may have used several brands of caps. For example, a radio I know well, the Westinghouse "refrigerator", has multiple brands of caps. I have had as many as 3 of these on the bench at one time and many more at other times. Some have Solar caps some don't and some have a mix. I think that I posted pictures of the "underside" of several of these.

Another large manufacture that did this is Emerson.

This applies to mostly 1930s radios.