Found this nickel today. . Looks like it was smashed. . The obverse has bottom half smaller, dime size. The reverse top half dime size?
It looks like it was either smashed so small it is no longer visible to the eye, or you forgot to post pictures.
I acknowledge that I am still learning, but the dark line on the reverse looks like the place that the metal "hinge" of the lamination would have been. The strike gets more blurry towards the rim because that metal didn't transfer the design well. Eventually, the metal flake that used to be there came off. That is my theory. I look forward to other responses.
Looks like it was partially dipped into some corrosive liquid and suspended that way for some length of time before being removed. PMD.
When you say "smaller (dime size)", do you mean thickness? If that half of the coin is thinner, that and the way the detail is distorted definitely point to corrosion.
It could have been struck thru a thin cap or just struck thru grease. The opposite area of the obverse also shows some distortion in the devices, I am leaning towards altered surfaces.
The black line looks like sulphur damage from a rubber band being around a box, envelope, container that the coin was in at some time.
