Raised Circle In The Field Of A Nickle

Hi don

I don't know what it is, but I think it must be damage to the working die itself. I have nickels in a few years between 2002 and the present with this very same marking; some coins have only one circle, others have a few, and there are slight variations in size as well. The reason I think it must be a mark in the die is the fact that a couple of the nickels of the same year have these rings in the exact same spot on each, although from year to year the spots are in different places.

So what would leave rings like this on the die? They look like bubble rings to me, so if the die was cleaned or otherwise exposed to a caustic element or acid that left small bubbles, and not properly wiped off, I suppose that a small ring might be eaten into the face of the die. I'm not basing this theory on anything but conjecture, but it sounds plausible at any rate.

Pennyman, what do you mean by "other pictures"? Of the same coin or others I have with the same marking?

Also, could you post a picture of the entire coin showing the location of the circle?