PhotogHobbyist wrote:
CHG_CNON, every Pentax lens I currently or previously owned, has, or had, a very similar "manual aperture prong poking out" and they all worked fine.
I will apologize to all, I had not tried it on my film Pentax cameras. It will mount and function as it should, so I'll remove the item from the selling thread.
Thanks for everyone's comments and advice.
I tried to hedge. No 1987-onward Canon EOS body could accept a lens with that prong. The entry-level Nikon digitals also would reject such an appendage. I'm not sure about their higher-end Nikon models, even it was an F-mount, but I think it would be a problem there too. Glad the mystery was resolved.