You are referring to the two leaf-shutter lenses, being the 90mm and 165mm (both f4). These are handy for raising the 67's pitiful x-sync from 1/30 to 1/60, 1/125, 1/250 or 1/500, by direct connection of flash to the lens (in leaf shutter mode).
There is still a fundamental requirement for a shutter in the camera body even with leaf shutter lenses (which can be used as normal lenses at any other time). In leaf shutter mode the camera-side shutter speed is set to 1/8 second while the leaf shutter on the lens is set to your desired sync speed (as mentioned earlier). You think that's all a bit confusing? Try doing it in a hurry! And if you do get it wrong, and do not follow procedure, it can damage the leaf shutter, the mirror, the camera shutter or all three!