This tube is in perfect mechanical condition, and comes with the original instruction manual plus a falling-to-pieces box that could easily be reglued. Or 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 tube has absolutely minimal signs of use other than slight marking on the mount.
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.