Between the Selectric and the Model F was another IBM keyswitch design known variously as the "Beam Spring" or "Keyboard B" which was much closer to the Selectr

Between the Selectric and the Model F was another IBM keyswitch design known variously as the "Beam Spring" or "Keyboard B" which was much closer to the Selectric in feel. It even used the same keycaps as the Selectric. The Model F was introduced as easier to manufacture and more compact. See: https://deskthority.net/wiki/Beam_spring https://deskthority.net/wiki/Beam_spring