Well - I think you may have found a genuine error I asked to see the full coin because I thought perhaps the coin was struck with low pressure. But the detail seems to indicate otherwise. Since I'm not really an error guy I may be wrong - but I think that is a partial collar error.
Has that coin been bent and straightened? I'm looking at that bent streak of light on both sides. Also, have you weighed the coin and measured its thickness? The picture looks like it may be just about double thick - if the weight is double that of a regular coin could it be that two planchets got crammed together in the coining press?
I'll take a guess at it. I'll say the the coin was struck on a planchet that was punched out of stock that was rolled thick. Sometimes caled a "thick planchet" error. (just a guess)
It could be struck on a planchet punched out of rolled-thick stock. You must weigh it to see. I don't see much evidence of finning of the rim, so the thick appearance is unlikely to be due to excessive striking pressure. My guess is that it's normal weight and that we're dealing with a strong strike in combination with abnormally deep rim gutters. You see this occasionally in Lincoln cents. The year 1991 was a pretty productive year for these sorts of "errors".
Unless the weight comes back high, I think it is simply a well struck coin. Usually cents aren't struc well and the edge never fills properly and can be seen in the first picture by the left hand coin. It show the typical thin flat edge and bevels up to the top of the rims. As the pressure of the strike increases that flat edge becomes wider and wider and te bevels less until the edge and rim met in a squared edge like that seen on a proof coin. If the striking pressure is increased still further THEN finning will begin occuring. Proof cent planchets are the same size and weight as those of business strikes but if you look at te edge it will be very similar to the coin pictured here.
