Mamiya SX lenses 1.8/55mm, 2.8/28mm, 2.8/35mm, 2.8/105mm, 1.7/85mm, 2.8/135mm and 3.5/200mm.

Mamiya Sekor SX lenses were made in a focal lengths from 14mm fisheye to 800mm super tele. Totally 20 different lenses including one zoom and one macro lens were built. It is said these lenses were built by Mamiya itself, and not outsorced as some of the earlier M42 lenses for the Mamiya TL / DTL series. I have tested six of them, shown above. Most of them are as good or even better than the contemporary Canon FD / Konica AR / Minolta MC / Nikon AI / Asahi-Pentax and Zeiss CY lenses. 

The SX 2.8/28mm, 1.8/55mm, 2.8/135mm and 3.5/200mm as well as the 90-230mm zoom are rather common and easy to find (about USD 50). The 2.8/35mm, the 1.4/55mm, the 2.8/60mm Macro and the short teles 2.8/85mm, 2.8/100mm and 2.8/105mm are more expensive (around 100-150 USD). All other SX lenses (such as the 14mm Fisheye, the 4/21mm superwide, the 1.7/85mm portrait and the 5.6/300mm, 6.3/400mm, 8/600 and 8/800 tele lenses) are quite expensive - roughly in the 300 to 600 USD range.

Even though these lenses are M42 lenses, their adaption to today's mirrorless cameras is not as straightforward as one might think:

 1) The SX lenses have no manual aperture mode. You need to get a M42 adapter with an internal lip / ring which pushes the aperture plunger into the lens, thus allowing manual operation of the aperture

 2) The aperture ring has a minute pin on its inside. This pin was meant to communicate the aperture value to the camera (open metering system!), but now it interferes with most of the M42 adapters I know. Therefore I have machined a common M42 adapter to allow for enough space for the pin; there's no interference possible any more