Over the years Clad Coins such as Quarters, Dimes and Half Dollars tend to change color when exposed to the Environment. Not a Mint Error... as stated all Environmental Damage. I should say Nickels also, even though they are not Clad, will suffer the same due to ED
You should find this post interesting. https://www.cointalk.com/threads/environmental-damage-or-works-of-art.289634/
As mentioned, these are environmental damage, but the dark tone on the 1989-D is neat looking. Worthless, but cool looking.
