A few photo's to replace Photobucket links.
I would say just leave the metal alone. The discoloration is just cosmetic most of the time, and it adds patina that shows the age of the jacket. You could try nevr-dull but I'm not sure if you would want to get that on the leather so you would have to be careful.I’m probably asking a question that will make some shudder, so apologies, but could anything be done to clean the metal parts up? Or just wear and use the jacket? I’ve never hankered after an original because of it looking (and pongin’?!) 70 plus years old, I like ‘em looking like they’re used through the 30’s and 40’s, but if I could find one looking as nice and clean as this I just might be tempted!
Great job on replacing the knits 2BM2K. Now the jacket looks even better - an original that's a wearer. A stunning jacket! Enjoy it and wear it in good health.