This is one of the things that confuse me more than anything. If you search for annealing errors or improperly annealed planchet you will get a wide array of colors that just look like environmental damage of some type or another to me. I'm pretty sure this one is just environmental damage of some kind, even though it looks like some examples of improper annealing, but how do I tell the difference and know for sure what I'm looking at?
So something like this? I had this one pegged as definitely environmental or chemical damage. If it only affects one side then this one fits the bill.
I've been trying to sort through some of my dad's old coin collections but I have no idea why some of them were kept. Some are labeled that I understand and a few are just bagged with no lable and some are just loose thrown in randomly and even several that just said PMD Joe. Maybe I should just stick with the little I know, lol
Have a look at this thread. Pay attention to Fred's comments. https://www.cointalk.com/threads/2017-d-new-jersey-ellis-island-improper-annealing.307775/