I owned an original Jerger. Purchased in Berlin when I was in the Army in 1965-68. I also had a German winder alarm clock which I used overseas.
The accuracy was astounding.
I am not into Physics or clocks. But I was told overseas that gravity affects
winders. I have no idea if the statement is true or false.
But I am aware from friends who wear those $300 to $1000 watches that they need to bring them in to a watch maker once a year for calibration.
To make Chess clocks perfect, possibly they should have Casio make Chess clocks. I wear a Solar Atomic Casio, an $89 item, which needs no calibration, no winding, no battery, and is adjusted by a signal from Fort Collins. The only thing I do is leave the watch by a window when not in use to recharge the solar battery. Note that there are battery operated atomic clocks, I own three and they never lose time. The same for digital cable box. Are chess clocks behind the times?