@Oldfordman, You bought this set because of the toned nickel. It was an eye appeal purchase. Don't agonize over it. If beautifully toned proof nickels were common, everyone would have them and you wouldn't have noticed this one.
Eye appeal is the beating heart of numismatics. It's what sets apart a fantastic coin from a decent coin. Here's the bottom line question: since it is
your collection, do
you enjoy having this coin in your collection? If so, it was a fantastic purchase, and the other coins in the proof set are nice tag-alongs for that purchase.
I, too, chase the eye appeal coins. In my case, it's
Buffalo nickels meeting my four very specific criteria. I buy coins that others might not snag, and I pass up many coins that others might buy. Don't be afraid to trust your instincts about a coin.
Again, you are in charge of your collection. You know what you like. That experience matters.
Well done. It's a really nice coin!