The F2 still has a non-dedicated hot-shoe, that accepts all non-dedicated flashes.
The 155A is already dedicated (to the Canon AE-1), as it got two additional contacts at its hot foot.
One sets the synchro shutter speed, the other the aperture, that has been chosen at the flash.
But as both additional contacts do not interfere with the hot shoe of your camera, you can still mount your flash on your camera.
You only have to set speed and aperture manually at your camera.