Quote Originally Posted by Charles Wass View Post
All Canon manual focus lenses FL and FD, both old and new, are breech lock type. Canon did not make a normal bayonet type. The register surfaces do not move against each other when the lens is mounted as they do with a normal bayonet; that is the whole point of the breech lock. In the case of the later FD type the whole of the barrel rotates to lock rather than a chrome ring.
I guess this is a bit tricky:

Concerning the mechanics of the coupling itself you are right. All FD couplings are not a bayonet mount in the way other bayonet mounts work (with friction between the distance-critical parts at body and lens).

From the user's point of view though the new FD lenses have true bayonet mounts (concerning handling).