Ok MagusAku, this might help you get out of your doldrums - see what a big boo boo I did...
This is a Vivitar 135 1:2.8.
I *thought* it was a Pentax but it turns out the listing said everything BUT Pentax.
I've squished it onto my k100d, and it fits but it's soooo not secure.
The Bayonet is on the opposite side of the red dot compared to our bayonet mounts.
There's also a little sticky bit to the right of the bayonet. I've taken some photos for you to look at.
I *think* this is the Nikkor mount. Am I correct?
The lens is in mint condition (shocker!) except for a little mark on the rear element which I initially thought was a scratch. But after rubbing it with a lens cleaner wipe it's just about all disappeared. There's only a slight mark left now. So who knows what that was... outside glass fungus?
no idea.
I've tried to take a few photos and the IQ looks great. But I'm really worried about the security of that lens... It fell off in my hands twice while I was trying to shoot!