Found this on the Goodwill auction site one morning. I'd been looking for one of the cameras on a low priority basis, but the microscope adapter made it worth getting now.
Nikon M-35S with PFM Microscope Adapter by P F McFarland, on Flickr
The adapter has the interface with the scope, plus adds a shutter (which the camera lacks). The camera, which was introduced in 1964, can be switched from 24x36 to 18x24 frame size, and is based on the 1960 Nikkorex 35. There was also a version that is only 24x36. With a standard LTM screw mount, it could be used for all sorts of scientific endeavors, including astrophotography.