Maybe nickels are sometime in lunar phases, check it next week, that dark area may be gone. :smurfy: Now seriously, I thought it might have been in a 2x2 but was trapped for awhile with it partially under the circular window? Maybe it has something to do with the annealing process and it was wedged someplace and that area was over heated? I don't know the answer, but maybe someone will. If it were only on one side I would say another nickel lay on top of it for a long time and the environment it was in caused the exposed area to tone or darken like that. Finally, maybe someone deliberately artificially toned it while not letting certain areas become toned.
We can rule out someone dipping it in a chemical (by itself) because it wouldn't result in an arc. Suppose someone sandwiched it between two other nickels (which didn't line up exactly from front to back) with that portion protruding and then dipped it in some kind of chemical. Chris
it toned while stacked with other nickels, like when someone spilled soda on it. the coins above and below it protected part of the coin.
