Thanks guys... yes it has the Nippon Kogaku logo, but isn't a 64xx.xxx SN, no red dot, no tick mark lenses... way, that would have cost me a lot €'s more and I'm not going to be a Nikon collector! 😉
Probably it was sold as a set in 1965 (year of my birth) and used as such: 1 camera/prism - 1 lens. If I didn't know where it came from I would believe it was pre-owned by a German doctor!
I've searched for a while around with finders. Finding a good black unmetered prism will probably cost more than I paid for the whole set, and I'm even happy it has TTL metering at all. The Photomic FTn would be a better user prism and looks better, but otherwise somewhat historically uncorrect, so probably I leave it as it is.
Favorite to shoot with my small bunch of NonAI-lenses is the (center-weight metered, AE) Nikkormat EL anyway... (hell, are they cheap)
Of course, the S2 is the cutiest of all and used most!