I have recently acquired a 2020 silver proof, 2020 proof, and 2021 proof sets, all of which have haze and/or spots on the Sacagawea dollar, and both the clad proof sets have a hazy penny as well.
What causes this? Is it just water or other chemicals not getting cleaned off before the coin is packaged? On some coins the toning seems to radiate out from a black spot or other speck on the surface of the coin, on others the spots can appear as "shadows" where the coin is toned all around it but not inside the spot itself, like on the 2020 Silver Proof Nickel shown below.
2020 Clad Proof


2020 Silver Proof


2021 Clad Proof

What causes this? Is it just water or other chemicals not getting cleaned off before the coin is packaged? On some coins the toning seems to radiate out from a black spot or other speck on the surface of the coin, on others the spots can appear as "shadows" where the coin is toned all around it but not inside the spot itself, like on the 2020 Silver Proof Nickel shown below.
2020 Clad Proof


2020 Silver Proof


2021 Clad Proof



















