You could probably use them as general purpose lapping plates. I don't suspect it has to be used only on an auto. I may have bought it for that price just to put on the shelf so when I need it 10 years from now, I've got it.
As for the name change, I think that probably happened before 1938. I've seen the American Bosch name on radios from the late 20s or early 30s. I never looked into the company history so I couldn't guess as to when exactly it became that. I don't happen to own one so it was never on my list of things to dig into.