Going through a jar of wheat pennies, I noticed a flaw that I could not identify. Not even sure how to describe it... picture a wire 'flue' brush (very small) brushing 3 consecutive grooves in the back of a coin. Now, my first thought was that it happened post mint, but then I looked a little closer. If it was post mint damage, wouldn't it have shaved the lettering off as well? I know this is a very poor picture, but there are clearly raised letters inside the grooves. Any thoughts?