Canon FL lens mount

Canon FX with FL 50mm f/1.8

Canon FL refers to a lens mount standard for 35mm single-lens reflex cameras from Canon. It was introduced in April 1964 with the Canon FX camera, replacing the previous Canon R mount. It was in turn replaced in 1971 by the Canon FD lens mount. FL lenses can also be used on FD-mount cameras.

FL cameras

FL 58mm f/1.2

FL 200mm f/4.5

Focal length(s)	Aperture range	Macro	Super Spectra Coating (SSC)
85mm	1.8	No	No
100mm	3.5	No	No
M 100mm	4	Yes	No
135mm	2.5	No	No
135mm	3.5	No	No
200mm	3.5 I	No	No
200mm	3.5 II	No	No
200mm	4.5	No	No
300mm	2.8	No	Yes
300mm	5.6	No	No
400mm	5.6	No	No
500mm	5.6	No	No
600mm	5.6	No	No
800mm	8	No	No
1200mm	11	No	No

The FL 19mm F3.5 (not the 19mm F3.5 R) was a true wide angle (short focus) lens. Its rear projected far into the mirror box on an SLR, and because of this, it could only be used on a camera with mirror lock-up (FP, FX, FT, F-1 (old), FTb, EF). It could not be used on either Pellix model.
The FL P 38mm F2.8 also projected into the mirror box. It was specially designed for the Pellix and could not be used on any other camera because the moving mirror would hit the rear of the lens. This lens had a longer lens mount index (the pin on the back or the lens at the top), that only fit the deeper cutout at the top of the Pellix's lens mount, thus making it impossible to mount this lens on any other camera.
the FL M 100mm F4 was a special purpose bellows lens. It could only be used when mounted on a bellows, such as the Bellows FL, because it lacked a focusing ring.
The list is complete.