That button is used to change the time chime music. There seems to be a switch that can turn on or off the time chime. If you look carefully, you can also turn off the night time chime function. If you can't find any switch, that is There is no shutdown function. Report every hour. If it does not tell the time, it means that the switch contacts built into the movement are defective, so replace them in time.

If you can't find it, you can find a merchant to replace it with a new one. They just say that it can't be used normally if it doesn't tell the time on the hour.