Loosing 4 seconds per day (28 per week) falls within the bounds of accuracy required of a Swiss certified mechanical chronometer and is pretty good. https://en

Loosing 4 seconds per day (28 per week) falls within the bounds of accuracy required of a Swiss certified mechanical chronometer and is pretty good. https://en.wikipedia.org/wiki/COSC https://en.wikipedia.org/wiki/COSC [I made a similar comment further down.]