This tube is in perfect mechanical condition, and you can download a copy of the Mamiya instructions from this website. This tube is in barely used, near mint condition overall.
The 3-S is the later version of the No.3 tube and was redesigned to prevent any of the vignetting problems that could occur with the original No. 3 tube. Apart from that there is not a lot to say – the aperture control works perfectly and the ring works fine.
This extension tube will give you 0.44 to 0.60x magnification with a standard 80mm lens. I tend to use this and the #2 ring just to get a closer focus with my 150mm and 210mm lenses – it is small enough that it is no problem to carry around in case you need it.