I found this 1964 D in a roll I had since way back then. It seems to have imbedded grease or dirt that has flakes of copper included. I don't see it as coming from circulation. I don't think it was ever in circulation. Opinions are very welcome.
Could be. The spots appear to be embedded grease. The flakes of copper are actually floating in little specs of grease. I took one off very easily with a toothpick.