The Pentax MF-1 is a scientific camera made by Pentax and based on the body of the Pentax ME.

It has a special finder with a round image field. The image is aerial, there is no ground glass. It has a spot meter, the manual speed is 1/4 instead of 1/100, and it has FP and X sync.

(This info is based on a post by Gene Poon in the PentaxUsers Yahoo Group.)