Inspired by this, I decided to build my own chain clock.
This was an easy project, since you can purchase AC synchronous motors which are geared to run at 1 rotation per hour. If you want to add additional gear train, you can get other speeds. These motors keep time based on the 60 Hz power signal, which in most 1st world countries is controlled by an atomic clock so is quite accurate.
After I built it, I found that the clock does not give a good indication of what time it is beyond the hour, so I added a “pendant” which shows the exact minute.