Hi Jerry - i was wondering about that myself. My buddy who was helping me (my paint/bodyman friend) said it was some kind of epoxy finish that didn’t scratch very easy. It appears the Inside is galvanized or similar.
i did some checking online and bought it from carparts.com which happens to be from/or a subsidiary of J.C. Whitney. It seems to be identical to the original in every respect even though it was made in Taiwan.
Thank you Ulf. It looks like it might be made of rubber?