can someone nicely explain to me why some Lincoln cents between 1994 and 1997 have such dark fields, almost prooflike, but not all of them? Did they all look like that when they left the mint, or whats the deal? Here are three that all look different from 1996:
Copper is the most reactive, well except maybe the manganese in the dollar coins, of our coinage metals. So the least little thing causes it to change color. It can be something as simple as differences in the air from one town to another. But it can also be the metal itself. Copper from one mines is a different color than copper from another mine. Even once refined and purified it is still a different color. Same for gold and silver even. Even when considered pure, there are still trace elements that change the color.
In the case of Zincolns, it's mostly due to differences in the planchet plating process. As the acid baths become contaminated with different trace metals, the surface appearance changes.
