Yep, as I said, 70's - 80's.
They could be a pain sometimes, refitting the door. Get 3 clips engaged ok, but the 4th won't lock. Undo a couple, then one of the others wouldn't lock.
I never did like then.
Also, the triangluar heads weren't very deep, & if they gor worn & rounded on the corners, the cab key wouldn't grip, & just jumped off.