Ah, thanks for explaining! That makes it much clearer. It looks like there was either corrosion or maybe verdigris or debris was on the coin at one point and fell off.
the guys are telling you the truth . your coin is just a damaged coin , the round spot on and beside the R is from something like maybe glue has come loose and fell off. this left the bright spot because the foreign material was protecting this area. also your cent is badly damaged in other areas from many years of use. when you learn more about error coins then you will know what folks are saying was the truth .
Does not look right, to be a Rockwell hardness tester error in the planchet (prior to the strike). I can't quite tell with the lighting, if the feature we see is incuse or raised... Until I can see a better microscopic photo, I am going to reserve my judgement as post-mint damage. In fact, it looks just like old world coins that had been drilled, then filled and retooled, but when I zoom in, all I see are pixels...
I'm not so sure it's PMD. The metal inside the top of the R throws me off. However, the big hit on the U puts PMD back into game for me. Which coin is this? I am having a hard time guessing the size. Is it a cent? Whatever the case, here is a closer view.
I just don't understand what error it could be if it WASN'T PMD. The odd discoloration and weird darker ring around the anomaly makes me think that there was something stuck to it soon after it was minted, and it circulated, adding wear and removing the luster from the rest of the coin, while the area underneath the crud didn't tone and circulate consistently with the rest of the coin, hence the obvious difference when it fell off. It revealed the "preserved" area, so to speak.
