I buy scopes off eBay and various classified sites and the best bargains are those scopes which have bad ring marks.
I'm not talking crushing or denting tubes but normal to severe ring marks such as you'd find on scopes tightened by Bubba.

My wife uses these foam pads sold as Magic Erasers from Mr. Clean. I tried these with a bit of water and a bit of dishsoap and with a little elbow grease even bad ring marks virtually disappear.
I was amazed how well these worked.

Link to Mr. Clean Magic Eraser.

http://www.mrclean.com/en_US/magic-eraser.do

There are other brands out there as well and they work too.

The Chosin Few November to December 1950, Korea.
I'm not one of the Chosin Few but no more remarkable group of Americans ever existed.