Hi, thanks for having a look at my thread! Facts: * I've bought a second hand unmarked wall clock. * Regulated it to 7200 beats per hour (or 2Hz), and got it within about 30 seconds a day with a phone app (see image). Problem: * Now as it's running it seems to be about half an hour a day too quick, despite the timing on my phone showing only about 30 seconds a day. What I've tried: * I've tried checking the regulation again and again. * I've checked the phone app against a computer generated 2Hz beat, and it checks out fine. * I've checked that the clock is fully wound. Any help would be greatly appreciated, to be honest I'm totally flabbergasted. Could it be that there are some clocks that have some wierd beat of less than 7200 per hour, but more than 3600?