Originally Posted by Denis
It is typical of lenses with an extra pin where the auto focus screw is, Ricoh(mark pk-r) lenses have this pin. You could have used a filler guage to unlock the lens, slide it in betwee the lens and body, where the AF screw is, wigglethe lens until it frees the pin. Lots of post requarding this procedure is available on the net.
The pin can be removed I did it on a Tokina: