Those of us that have collections helped Adam and Ole put together a review section with the Pentax (Asahi Optical) m42 bodies in it. The S3 was marketed in the U.S. as the H3. I think I have one of each. At any rate the PF review for the S3 is here:
Pentax S3 (H3) - M42 Screwmount Film SLRs - Pentax Camera Reviews and Specifications
There are at least 3 books out there (though hard to get hold off) that have some info on the m42 bodies. One is by Fred Sherfy (
Asahiflex and pre-1959 Pentax Cameras), one by Gerjan van Oosten (
Asahi Pentax Screw Mount Guide), and another by Danil Cechi (
Asahi Pentax and Pentax SLR 35mm Cameras 1952-1989). Since the S3 came out in 1960, the Sherfy book doesn't cover it.
Fred Sherfy has an informative web site on the early M42 stuff.
http://www.concentric.net/~sherfy/special1.html
I personally have kept up with serial numbers etc and would guess that 1 in 20 bodies were black for the S3. However, I seem to see more black H3 than the S3 but that could be because of the H3 being marketed in the U.S. According to Gerjan, there was NOT a price increase in this model for the optional black which is unusual.