As for darkening finish, keep in mind that even the finishes used on radios do darken with time, though usually only to a yellow-orange. Also, some colored finishes on radios were intentionally somewhat opaque, as they were to hide things like the end of plywood, as I have mentioned before (if not ordinary plywood, at least the layers of veneer and such). If one suspects the finish to be darkened by something other than the original tones added to it, you can use a good grade of furniture soap. This can really brighten up a finish. I have used a foam product in an aersol can, but I don't recall the name at the moment, and the can is from the 1970s (still works). At any rate, it says on the can that it is for fine furniture, and it does wonders for stripping old wax and dirt from the varnish without ruining the varnish. The residue removed is often brown, which says something about the darkening of the piece.

As for refinishing sets, it is a bad idea to refinish a set that is in good condition, but I strongly encourage everyone to rebuild cabinets of those beat up sets that look atrocious (veneer missing, cabinet broken in places, heavily water damaged, etc.). It can be a real treat restoring such sets, because when you take pictures (before restoration) and show them to people, they will be stunned at your fine results. You will also be rejuvenating an otherwise worthless set. Of course there are sets that are extremely rare that may or may not be reduced in value by a refinishing job even if they were originally in horrible shape. I do not know of any, though. Taking beat up sets and making masterpieces out of them can also be a means of obtaining an otherwise unaffordable radio, though if the chassis of such a set is terribly rusted, and you are required to polish and replate the entire thing (along with replacing useless parts), you may pay more in the long run for the set than you would for one in good condition. Still, it is great to keep as many of the old radios around as possible.

Thomas