When a planchet doesn't get into the coining chamber, the field of the die slam together. It makes the outlines of the devices transfer onto each other. To remove this, they polish the dies to remove the clash marks. Removing part of the dies outside (field area). When this happens many times the devices start of suffer on the die and they get thinner or missing in later die polishings. They are done by the mint to cover these clash marks.
If the public polished it would be smooth and not raised on the coin. Raised on the coin is a die issue. Hand polishing the coin would remove/disturb the rims of the coin.
Edited by coop
10/24/2013 3:00 pm