I just joined.
I bought my K-50 about a year and a half ago with a DA WR 18-55 lens.
I find the lens unable to get any better than my vision across the soccer field when
my daughter is playing.
On a lark today, I bought a Komura Komuranon 821-S f=80~200mm 4.5-22 lens at the Salvation Army for $20.
The flanges on the lens line up with the openings on the camera (the red dots don't) but it will not twist and lock.
I am clueless about if it can be made to fit.
The lens came without documentation, and a web search is pretty sparse.
I am not sure what type of mount the lens has, or if it already has an adaptor.
If the lens has an adapter, I do not know how to remove it.
Very dangerous lark, Zuke. Carefully unscrew this lens and return it to the flea market before you ruin the camera. Then go to pentaxforums.com or eBay and search for "K-mount" compatible lenses. Nothing else will fit.