Are all outer shells of the '41-'46 hub caps made out of stainless? I tried polishing these 2 dull ones again on the bench grinder with the buffing wheel. They look to be stainless around the edge where they're crimped but they can't be. I've polished a lot of stainless over the last few years and always end up with mirror finishes even on some bad looking metal. These 2 caps won't even come close to polishing up.