I was at my local electronics store yesterday and I noticed a domestic ultrasonic cleaner. The advertising said "ideal for cleaning watches" there did not appear to be a lot of information, other than 54khz, you place the watch to be cleaned in the machine and a few minutes later you have a clean watch.
Has anyone used one, does it work, any potential for damage, (standing waves). I understand that usually there would be a medium for the ultrasound to travel through, some sort of coupling water? gel? I am thinking that it would not penetrate the case or crystal but if it did would all the small oscillations cause damage to a mechanical mvt.