This is a really excellent condition Mamiya 645 55mm f2.8 C lens, including both caps.
This lens has is in perfect mechanical condition. No problems at all, aperture really fast without any sticking. There are only really minimal signs of use, just the usual paint loss on the mount. This lens has superb glass with just a trace of very fine dust that will have no effect at all on your images, and no other issues.
Now seriously hard to find; this is a really superb lens and you will not easily find a better example.