Airstream started clearcoating(plasticoting) in the early 60's. They
never anodized the aluminum. Your coach, after 40 years may or may not
have clearcoating. An easy test is to put a dab of toothpaste on a white
rag and rub an inconspicious spot on your airstream skin. If the rag
turns black you don't have clearcoating there. If it doesn't go black it
is coated. A 40 year old airstream that wasn't clearcoated should be
dull gray by now. Of course someone could have polished it before.