Cleaning A 43 Steely? Any Tricks?

Thanks, I'll check it out. Normally I would not either, but these were so bad that I could barely read the dates. I soaked in a weak Acetone bath for about 5 minutes and rinsed and dryed with a towel, it helped alot, but would love if there was a trick to get some of the shine back. I can see it lying just under a layer of grime and rust, but it's out of my reach, lol

Sort of a waste of time and money. Those in really nice shape sell for from $0.25 to $1 at most coin shows, flea markets, etc.
The problem with cleaning those is they are made with rather cheap Steel, covered with Zinc. Once the Zinc is gone or some of it gone, the Steel starts to corrode, Oxide, rust or whatever you want to call it but it is now on it's way to coin heaven. If you really want to experiment, there are products on the market in many hardware stores for removing rust from piping. Also, those solutions for removing dirt, grime, oxides from screen doors and window.
You could spend a lot of money trying to remove the rust but would only end up with a 1 cent coin worth 1 cent.

The "build up" is zinc oxide from corrosion on the zinc plating, remove that and you will have a raw steel coin that will turn into a pile of rust. Zinc plated steel was the worst planchet material ever used for US coins. Making matters worse, only the metal stock was plated so punched blanks had exposed steel on the rim causing them to rust even faster