Fantastic information, thank you very much, The Zigmeister!
I'm a bit unsettled though: Been to my AD with a recently purchased Gen IWC (cal. "7922", enhanced 7750) that was running since 2004. It keeps time very accurately (-1/+1 sec when placed face down at night). The lady at the AD told me that no service was needed. They only recommend service when the watch performance gets out of line.
No regular service for gen movements then? Any thoughts on this?
Yours kindly
Valerian