I just want to share some experience...... Today I bought a Junghans alarm clock at a flee market. It came with a music unit (Sorry I do not know what it is called in english.) I replaced a broken hair spring and the watch started running..... Great! Then I startes cleaning the watch and among other things I disassembled the "music unit". The barrel with all the small pigs as well as its casing went into the ultrasonic cleaner. After 5 minutes I checked and was not happy! The loution was dull and the barrel has some internal stuff that started to dissolve. The housing was dark and my fingers was smeared by some geggy stuff. The geggy stuff came off with dishwashing loution and I could polish the metall. But my message is that you might want to be careful when cleaning this type of clock parts.