[RodB]

Jim, your capacitor is probably a mica-mold. At some point in time "they" sold a capacitor that was meant to look like a mica cap but was made of paper and foil just like the paper/wax ones.

You can clean a tuning capacitor with electronics spray cleaners depending on what's attached to the plates. Some radios spent a lot of time in the kitchen collecting a layer of oils and grease. Only way to get rid of that is to send it back to the kitchen for a session with the dishwasher. Some use a brake cleaner spray, nasty. Something else you want to look at is if it has been mounted on grommets they may be hard or cracked, best to replace them. Of course the hardest part of removing the tuning capacitor is restringing the dial cord.