1936 S - Lincoln - Carbon Spots Reverse

What error or variety are you seeing?
John1

Staining/corrasion of some sort. Not an error or variety.
John1

that coin has been around a long time, who knows what it has been in contact with? Not a error, just discoloration.

Those are carbon spots. I'm guessing the Obverse and reverse view on the coin are the same color. The light on the obverse seems lighter. One had a stronger closeness to the light, or sheen off of the coin lightened the image. If you had an editing program like Photoshop, you could make them both the same color or enhance one to make them look the same. So what setup you used, is better on the second image. Always figure out why there are differences (or what you did differently) then continue to use the better setup. Always remember what works, and what doesn't. That is how you will improve your images. Soon you will be a pro image taker/editor/teacher as you will have something to show/explain/comment about.

Sorry to announce you that those spots are like the mushrooms for those coins 95% Copper, 5% Tin and Zinc. They damage permanently and nothing could stop them to go forward. Could be inhibyte for a small period of time but not permanently. The Tin attract the carbon ions and then the zinc ions come in action, Nothing to do for.

Carbon. The mushroom reference is more like an analogy - the carbon spots will grow just like the fungus in the cave.