Originally posted by boriscleto But if the 'Ricoh pin' is a rounded nub you don't have to worry about it.
This is a difficult matter. It used to be my practice to recommend total avoidance or surgery to avoid "Ricoh pin" peril. That is the safest route to be sure, though things get muddy when considering the benign version of the pin. Boris describe that version as a rounded nub. The examples I have seen have been a spring-loaded ball or rounded pin that extends a very small distance beyond the mount face and which easily rides over the edge of the AF drive well.
The dangerous version of the pin is an actual spring-loaded pin that extends a fair distance from the mount face. Both types are found on both Rikenon P and third-party lenses for the Ricoh P mount. The benign version (rounded nub or ball) can be safely used on Pentax AF cameras and should not be a cause for surgical intervention.
As always, I must add that XR Rikenon and Auto Rikenon and plain Rikenon are all safe and do not have the pin.
Steve