That mount is exactly the same as my Sears 50mm f/1.7 and Sears 50mm f/2.0 (including the red dot). I suspect its Tokina or Ricoh make. I do have a Sears 1.7 that came off a Chinon-clone KS Super II, and its mount looks nothing like that. The Chinon-clone 50 also has half stop aperture clicks which its brother lacks, and a closer MFD.
If you do a bit of local digging or prowl eBay enough, you could probably snag a manual 1.7 for half that cost. Both my 1.7's cost me $15 - one off eBay, one from a local Goodwill. My 2 manual 2.0's (Sears and Pentax-M) cost me even less, since both came bundled on cameras that cost $15 or less alone.
Last edited by Sagitta; 09-30-2012 at 12:31 PM.