Depending on what lever you're describing- There is a small plate with an actuator arm which clamps the disc brake on the drive shaft. This is present in all Nova models. (Worm gear/jack shaft bikes)
Some of the Nova bikes were equipped with a disconnect mechanism which allowed you to push the bike around without the belt/worm gear being engaged. That sounds like what you are talking about, since the brake is pretty obvious. Not all Nova's had that disconnect.
Richard Trotter will see this post and shed some light on the situation.