Quite uncommon very sharp,very well built precise Japanese lens. It hasn't auto-manual switch so to use on DSLR bodies need to prepare the lens or use newest M42 adapter with auto push ring.Very good performer one of the best 50mm M42 lens. I didn't find many information about this lens,so this is the reason why I think pretty rare. Perhaps more popular in Japan. I have pleasant experience all around, so I can't say more, grab it if you have a chance.