I've seen many Felsa Bidynators, and also quite some of their grandmothers Felsa 415, but I never came across a damage like this:
The watch is some 75 years old,
the chromed case is near mint,
the movement is clean and runs perfectly,
but the rotor seems exploded.
The lead inlay of the rotor has completely turned to white powder (likely hydroxide) and its grown volume blasted the side wall of the rotor away.
But whatever affected the lead in the rotor, why is the lead gasket for the back untouched, as visible in the pic?
No clue about the reason: Chemistry? Miracle? Aliens? Earth radiation? Mobile-phone pollution?
Regards, Roland Ranfft