Quote Originally Posted by zackesch View Post
A few days ago I got a vemar 135 f2.8 lens. At the camera store it was marked as an m42 lens. I received the pentax OEM k to m42 adapter and the lens will not fit. The threading is wider then the M42. The only other markings by the mount is "MA." Any ideas on what it could be?
The lens may be a T-mount lens. IIRC, the T [aka T2] mount is the same diameter as the M42, but the thread pitch is different [I think it's 1 mm for the M42, and 0.75 mm for the T2]

You may already have a T2 to K mount adapter if you have other pre-set or manual diaphragm lenses, slide copiers, etc.