A process in which the surfaces of a coin or a planchet are shined through rubbing or polishing. This term has both a positive and a negative context: In a positive sense, Proof planchets are burnished before they are struck. The procedure was done originally by rubbing wet sand across the surfaces to impart a mirror-like finish. In a negative sense, the surfaces on repaired or altered coins may be burnished by mechanical or chemical methods. For example, a high-speed drill with a wire brush attachment is used to achieve this effect.