It is NOT a PK mount of any kind. Even T-mount-PK adapters follow PK architecture. PK mounts have one bayonet blade substantially shorter than the other two, and with a lens-lock slot near the middle of the short blade. Exception: Some macro-tube mounts, and wide-flange no-infinity-focus M42-PK adapters, have blades of equal length; but they still have a hole or slot for the lens-lock pin to engage.
It looks more like an Exakta mount. One way to tell: measure it. The inner diameter of a PK mount is about 41mm. The I.D. of an Exakta mount is about 34mm. (I just now measured these.) Exakta-mount lenses can be quite easily (and non-destructively) adapted to PK mount. If you wish, I'll tell you how. If you don't want to bother, I may be interested in the lens. How is the lens labeled?
Last edited by RioRico; 04-24-2012 at 07:42 PM.