Originally posted by D1N0 Can anybody identify this one?
As soon as I saw the photo, and before I scrolled down to the bottom of your post, I thought: "Hey, that looks like that old Cosina 135mm that I used to have back in the eighties." So I think your research is probably right and that is what it is.
The bad news is that it wasn't a great lens, not very sharp and with low contrast. Although stopped down a bit and with the contrast boosted in pp, it might well work a lot better on a DSLR than it ever did on film.
Edit:
Here's a Kodachrome 64 shot taken with it.
I'm fascinated by that thing that looks like some sort of 200mm preset at the back of your group photo above. Any more info about it?