It is not repainted. How do I know? It is a picture of my watch It was bought from it's first owner and he hadn't done anything to it. When I got the watch, I just serviced it but case, hands, dial dial are all orginal and untouched. It looks exactly the same as the blue A3637 that is on Rössler's Zenith book.
I'd say that it has a Squale case. It is same kind that Squale used and made for other brands. If I remember correctly Squale made cases also for Zenith and this should be that one.