I have noticed on a few of my AU-UNC nickels that when tilted at an angle under a light, they show areas of hazy grayish colored toning/spotting. Is this part of the natural toning process or is it caused by dipping, rinsing or some other unnatural process, or perhaps just friction? All of the coins I am referring to are in TPG holders. One of them (not the one pictured as I don't have it accessible) has very pronounced spots of this type, one of which is visible even without putting it under a light. I'm curious as to how this affects the grade, particularly if showed up after being slabbed. Notice how this one has it on the high points of the head, but not in the recessed areas around the nose and forehead.
The spots are commonly referred to as "carbon spots". If they are large enough they absolutely can detrimentally affect the grade of the coin. However, I can't even see them on your coin so I think you are good. I have a 1939-D Jefferson Nickel NGC MS67 that has some light carbon spotting on Jefferson's forehead that can be seen with the naked eye.
He's not talking about carbon spots or anything remotely similar to carbon spots. He's talking about the large patches of different grey color that on his coin cover most of the head. If you have pictures of other coins with the effect you are talking about perhaps posting them would make it easier for others to better understand your question. To try and answer your question, I'm not sure what caused the effect you are seeing on this coin, but I understand what you are talking about. And yes, in some cases those areas where the color is different is sometimes caused by wear. Other times a similar effect can be caused by some sort of contaminant having been removed from the coin with acetone or some solvent. This leaves behind areas/patches/spots of a lighter grey color on the coin. They are lighter in color because that portion of the metal was protected from toning by whatever was on the coin, so once it is removed that untoned metal is exposed. They can also sometimes be caused by the coin having been dipped to remove dark or unsightly toning, particularly if the toning was patchy, spotty, or mottled. Based on your picture, which makes it kind of hard to tell, that may be what happened to this coin. As to how it affects the grade, that can vary greatly. If it was caused by wear rather obviously it should result in the coin being graded AU. If it was caused by cleaning (not harsh cleaning but acceptable cleaning) or dipping then it is mainly a question of how it affects the eye appeal and thus the grade, a matter of degree in other words. The coin may well still be graded MS, but not as high as it might have been if not for the patchy coloration.
Thanks for your reply! That is exactly what I was wondering about. This particular coin was graded MS65 by PCGS. The other one I was referring to where the effect is more pronounced was graded AU58. I would send a picture but it's locked away in the bank. Until now I didn't realize that nickel coins are dipped as well; I thought that dip was mainly used on silver.
