the seller can't tell me what mount is on this lens and I can't work it out either. Do any of you recognize this one: I have been told that dimensions on the lens are: "Filter thread is m31, the lens is 30mm tall--overall diameter (not the larger part close to the mount..) is 37mm. It is a 50mm f2" Some kind of cine lens? C mount? not suitable to cover fully M43 sensor?