Konica Reflex Hexanon ARM 1000mm f/8
It is believed that no more than a few dozens of these lenses were ever made by Konica. The price at the time would buy a modest car.
This large "mirror" lens uses a rear mounted bellows type focusing mechanism.
It and the larger 2000mm Reflex Hexanon are unique among "mirror" lenses, having some form of aperture control. At the rear is mounted a disc with, effectively, Waterhouse stops (various size holes) in it. It can be dialed into place, to achieve different aperture settings. Different constructions are reported.