Grease or oil on a coin,either from your hands or any other source can cause it to color or tone when stored overtime,in rolls or in storage. The dies are polished and greased at the mint.No,spraying them doesnt seem progressive,it would ruin the coin,not add to the value. That is normal toning,some can be quite desirable.
I think I bought someones returns. The first five rolls produced about 100 coins with this kind of color. All dates are between 1977 to 1983. I bought $30 so I will just keep on going. Some coins seem to be a little too shiny. Just checking. Thanks.
They simply have been stored in the banks temp controlled vault for years,I love getting boxes like that,wear gloves when dealing with stuff like that,you might find a gem or 2.