Originally Posted by joeyc 
What's the Ricoh pin you mention?
Rikenon-P/Sears P as well as third-party lenses labeled KR, PK/R, KA/R, etc. have a spring-loaded "pin" on the mount face that can jam into the AF drive gear of a Pentax AF body. In the worst case, the lens may have to be cut off the camera. Best case is that it causes no problems (certain designs only). These lenses can be distinguished by the presence of the pin and the "P" setting on the aperture ring.
XR Rikenon, Rikenon, and M42 screw mount Auto-Rikenon don't have this problem (all without the "P" setting on the aperture ring). Think "P" is "pin" is bad. There are illustrations on the Web (Google "Ricoh pin") that show the pin along with instructions on how to (hopefully) get remove your stuck lens.
Steve