Zenit-C (S) is very a compact SLR, which has two alternative lens as origin. The fixing is 39 mm Leica thread. In this case it has bigger lens, Helios 2/58, better known in later models. Work quality is good and it's very pretty, small compared to any similar western and far east item. The body has borrowed from some russian fake Leica - you can notice similarity to Fed 1F below on this page. It's very pure russian design, although base concept is well known.
If you are in need of more lenses, I think there is a reasonably priced set available.