Are you talking about the little black specks? I call them flyspecks, and I view them to be tiny spots of corrosion. I have never been able to satisfactorily remove them. They don't really affect the technical grade when they're that small. Personally, I find them abhorrent, and a coin has to be really, really special for me to buy it if these are present. I generally shy away from them, even if they're in first tier plastic. Especially being a 1950-D, with so many nice examples around, I would seek to replace it.