[morzh]

Here's a story about patina: about 9 or 10 years ago on "Antique roadshow" it was....

A guy found a large brass lamp in his attic. He cleaned it up and brought it in.

The expert tod him this:

First, he said, the good news: this lamp in this condition will pull about 30K on the right auction. (the guy's jaw started dropping).
Now he says, bad news: if you did not clean the patina off, it would be 90K.

So....be careful about cleaning old stuff, you could be cleaning lots of money right off.
(of course it works different with radios somewhat...still).