These clip-ons appear to be made for a CB500, but they are at a strange angle which makes me believe they are intended for another application.
There is a threaded hole in the bottom of the fork cap which fits onto the threaded rod in the fork tube, and another on top which bolts the clip-on to the fork cap. Does anyone know of a 35mm fork which would have the triple tree bolt further forward than this? On the cb500, there is very little turning radius.