In 1990 I bought a used Mamiya SLR with a Cosinon 28/2.8 Auto MC, M42. That lens differs from the common lens with the same name. It has another optics with 58 mm filterthread (instead of 52mm), and a longer focus scaled from 0.4 to 10 m (instead of 5m). The aparture has 6 blades.

In compairision do I find it to be sharper and to render a very good greyscale, while it in turn doesn.t perform very well with high contrast.

I have not been able to find any trace of this lens on the web, does anybody here know something about it?