Paint loss happens with wear and with time. It's why I think that it's a tough decision on whether or not to wear an original vintage jacket with leather patches. They don't last forever if they're being used. For instance, the below patches are both from the 765th Squadron of the 461st BG, 15th Air Force. One was on a guy's A-2 jacket that he wore throughout his service, and after as well. The other was from a guy on the same crew that never applied his to a jacket, and just stored it. The difference in condition is obvious.
[img][img]http://i57.photobucket.com/albums/g204/tulsaboy/765thpatch.jpg[/img]
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Original patches from WWII are incredibly valuable, especially if they come from particular squadrons or bomb/fighter groups. There are a bunch of avid collectors out there that will pay top dollar. I'd find one of their websites to see if they have suggestions on preservation. As with most any preservation effort, you don't generally want to try to clean them, use any chemicals on them, use any abrasive pads on them, or handle them more than you have to.
kevin