If anyone has lenses that have been butchered like that please feel free to send them my way
Skyntara,
I can almost bet that a Sigma SLR shooter owned that lens in the past. We have to shave off the aperture lever, along with the plastic part sticking up beside it.
Then it'll fit our Sigma's.
In the case of the 50mm f1.2 I believe that it'll hit the UV (dust) filter pictured here
before it'll hit infinity. So it's a useless lens for anything other than close up photography.
But most people wouldn't realize this before preforming the mods required.
The missing pin probably just happened, while preforming the mod.
Sigma cameras use a K-Mount (although a little larger than the Pentax, so a Pentax lens fits a little loose) and the electronics used in Canon lenses.
With a little work we can modify any new Canon lens to work with out cameras, and any Pentax lenses... which still have a manual aperture adjustment to work with our cameras.