And this is probably a FAKE black paint S2. According to the lens mount helical, this should be a "black dial" black paint S2. But the speeds dial selector is a (re)painted "chrome dial" one !
So, it's either a mix of chrome dial/black dial S2 parts fitted on an original black paint S2 body, or a "chrome dial" S2 fitted with a "black dial" S2 lens mount helical, and painted back in black by some aftermarket artisan... the bubbling paint finish making the latter option quite probable.
There are some clearer explanations about what a "black Nikon S2 black dial" actually is here :
http://www.cameraquest.com/nrfs2bl.htm