[Fisherdude]

I collect, among other things, old shortwave radios.

It's not at all uncommon for that old wrinkle finish to be permanently discolored by exposure to sunlight, who-knows-what under a bench in a garage for 40 years, cleaning agents, etc., etc..

The first suggestion is a good scrubbing with a NON-abrasive cleaner, such as Windex, simple soap and warm water, etc.. This will remove grime, cigarette smoke residue, and anything else that hasn't penetrated the paint. The use of any sanding paper, even 1000 grit, will destroy the finish.

After it dries you'll know what you've got. If it's still discolored, then it's permanent. Then you've got a choice between something a bit risky, or refinishing the cabinet. If you're talking about a section that has lettering, it's going to get very difficult.

Assuming you're talking about the cabinet, and not the front panel where the lettering is, here's something you can try. After you've scrubbed it with a cleaner, rinsed it, and let it dry, if it's still discolored you can get some color-matched enamel, thin it as far as the label says you can thin it, and then using a spray gun mist on the lightest coat you can make. That will cover the discoloration without filling in the wrinkle finish and making it smooth.

If you don't want to try repainting, you can try Armor-All. The purists will scream, but it will make the existing paint look pretty good. You do need to keep in mind that Armor-All contains silicones, which means that once you put it on, new paint won't stick to the old finish. So if you ever do decide to repaint the cabinet, you'll need to do some pretty aggressive cleaning to remove any traces of the Armor-All.