What Causes This Error Or Wear

Well grease can affect this area, but another thing that alters this area is vending machines. The fingers inside of the machines can scratch, alter, dent of ruin a coin. Note the tops and bottoms of the devices are normal, but the centers were altered? While I don't see coin scratches, I see the devices wider. Which is an indication that this was a Struck Through Grease issue on this coin. The more grease in an area of the deeper parts of the die, the less height the devices will have on the coin. So what could cause an even distrubution of the grease. Being wiped down with a cloth of a die worker. It would move the grease and the corners of the devices would probably wiped free with the cloth. (Or clean out with a wooden tool like a toothpick.)