Originally posted by pxpaulx Take the pin out, it ain't worth the hassle.
It's not the pin, it's the inoffensive nearly flush round ball of a "nub." Definitely a difference between the pin, and the nub. The nub is really no different than the other contact pins. To be fare though, I promise to give you props if I encounter an "I told you so" moment.
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To return to specific topic at hand, the P/KR mount IS the pentax bayonet, but with an extra pin that ricoh cameras used to transmit the aperture info. So other than being wary of that pin getting stuck (so removing it if it's the more dangerous of the pins OR if you're extra cautious), the P/KR mount is completely pentax mountable without an adapter.