The quarter has been in an acidic environment. The acid reacts more with the copper core than with the outer copper nickel layers.
At first I thought it might be a partial collar strike that had been soaked in acid. But I now I think I agree with the others that the copper was likely more reactive, creating that interesting partial collar appearance.
Only one, as long as they don't listen to poor advice from members who don't believe experts like Mike Diamond and Fred Weinberg.
New job and didn’t have time for my hobbies/passions sadly...but I’m back now, and I have a lot to show and tell