I was going through a bag of pennies to pull out the copper ones. I found a 1945 with what looks like a rectangular copper slag over the "rib" in pluribus. I want to keep this penny as a oddity. Do you think it comes from a stamping error?
Not a cud. A cud occurs when a piece of the die breaks off on the edge. You won't see flaking but instead an area on the edge of the Coin that was't struck because a piece of the die was missing. Also on a cud you would see a weak strike on the opposite side of the Coin in the same area as the cud