Did you get that metal detecting? It has that look. Vinegar will get rid of all the corrosion if you leave it in long enough, but it causes a lot of etching. I found a couple no date buffalos at the beach. They were so worn and beat up (AG-3 at best) I decided "what the heck" and left them until all the pink was gone and they were silver colored again. They definitely look better than when I started, but they look really weird now, so I wouldn't recommend it as anything other than an experiment on a coin you don't care about. I'll have to think about what to do if I get a corroded nickel that is of a reasonable grade.