For all those who might consider using a Timegrapher App. (setup of today as demonstration for this thread)
Put the headphone microphone below the crown, close the box for noise reduction,
connect the headphone with your smartphone, start the App. and you get such a screen
SD43, no full winding, dial up position, lift angle: 53 degrees, BPH: 28800
Result -> Rate: + 4.5 s/d, Amplitude: 242 degrees, beat error: 0 ms
It's really easy to obtain a "rough" overview from time to time.