I just found this penny yesterday and I think it might be a rpm. Its tough to tell in the pics but there is a small shelf outlining the right side of the D.
At first I thought it was only plating problems as there appear to be a lot of plating bubbles on the coin. But the mm could be some die deterioration , or a combination of the two. Not a rpm. Welcome to the forum!
Welcome to the forum,it can be so difficult to distinguish the difference's,I am still learning the basics(machine doubling drives me nuts) but it's thank's to guy's and gal's on here that share their knowledge to help us learn.(and desertgem is like a jedi in this stuff).Still a cool coin though and I would have thought the same as you.