Just back from service with Duncan at Genesis Watchmaking. It ended up going through a full service after all due to some rust on the parts linking to the stem, and is now looking resplendent fitted once more to the Chonostop deployant it came with:
2nd generation S.58 from 1960, made shortly after Zenith figured out that a rotatable bezel was a good idea.
Evening switch to new arrival: 1st generation pre-bezel S.58 with original brick-road bracelet. I don't think there was ever a watch quite like the "artist's conception" seen here.