I am not a collector but I do have several No. 2-1/2 Automatics. These have only a single spring loaded arm that captures the fence / lever. Not mounted but holding the lock up to my ear I can hear the fence as it drops down onto wheels when I move the cam, so it is a possibility. But then again it is a 4 wheel lock and gravity only fence. Definitely would need an amplifier as the feel is so slight.