ANDY
in no way does it hurt the coin!! i have been a goldsmith for 19 years, i have been cleaning coins and silver strikes in the ultrasonic for 10 years, all it does is clean the coin and remove the tarnish!! greatest thing on earth to clean a silver strike, the worse thing to clean a coin or silver strike is with a paste or silver dip, that will harm your coin!!! but a ultrasonic cleaner can not harm your coin in any way ,shape,or form! it works great with a little bakeing soda and dish soap mix with water in the cleaner, this will make you coin look as nice as the day it fell out of the machine!