Canon F-A

The Canon F-A is a 35mm SLR camera for ophthalmic examination ('Fundus photography': photography of the back of the eye, including the retina and macula and associated blood vessels.[1]), produced in small numbers by Canon in about 1980. It appears to be based on one of the mainstream A-series cameras (perhaps the AE-1: the controls on the left of the lens-mount are the same), and has a normal FD bayonet flange, but also several strange features: