Although it had an automatic diaphragm which stopped down and opened up again after the exposure, depth of field was not so easy. The Canonflex introduced what was to become the famous Canon breech lock mount. The selling point is you always have a secure mount, since any wear is automatically compensated for by tightening the breech. Real world, this system took took noticeably longer to attach or remove lenses. Worse, the extended pins and levers were unprotected without a rear lens cap.
Lenses have a different set of connections at the back.
Some will be OK, some not OK, so be careful. The removable pentaprism was very nicely done, riding on backward sliding rails like the Miranda Orion. This mounting system is one of the few areas that Canonflex excelled the Nikon F. A waist level finder and a 4x magnifier were also available. Focusing screens were not interchangeable. Today the removable exposure meter is rather hard to find.