Shutter preferred automatic exposure was achieved by setting the aperture dial to EE.
Only the EX-Auto and the prior EX-EE used these lenses.
They did not take Canon FL or FD bayonet mount lenses.
A needle in the window points to the correct aperture to set depending on the shutter speed you have selected.
In operation it is similar to the clip-on meters on the original Canonflex and other cameras such as my first SLR, the Pentax H3v.
It has a typical shutter speed dial, but the aperture adjustment is on a dial on top of the camera instead of on a lens ring.
The dial does not have all the intermediate apertures but you could read what they were in the viewfinder.
He knew the likes of Woodie Guthrie and was part of the New York folk scene in the early 1950s, and later part of the music scene in San Francisco and San Diego. (See, e.g., Fred Gerlach special - Blue Moment Arts, Obit: Fred Gerlach has Died, The Mudcat Cafe, R. Fred Gerlach was also amazingly talented in many other ways.
I bought the camera from his son David and also met Fred Gerlach's wife Barbara.
It is outside the mainstream of Canon SLRs since it had a unique lens system.