This is a really excellent condition Mamiya 645 55mm f2.8 C lens, including both caps.
This lens has is in perfect optical condition, and the aperture is really fast without any sticking. There are only really minimal signs of use, just the usual paint loss on the mount. This lens has very slightly stiff focus when first turned (really common with Mamiya 645 lenses) and then frees up immediately to work perfectly. There are no other issues.
Now seriously hard to find; this is a really superb lens and you will not easily find a better example.