Charles Leven's practice driver was covered under a British patent dated July 28, 1921.  Its built-in mechanism measures how far a golfer's practice swing would have hit a golf ball.  This mechanism, located in the top of the head, operates on the principle of centrifugal force with a weight and ratcheting device inside the head.  Pushing the button on the back of the head would reset the mechanism to zero, ready to measure the next swing. 

The example offered here is intact but is missing the small button on the back of the head. The 43 1/4" shaft and leather-wrapped grip is original as is everything else on this club. Even thought the mechanism is missing its reset button, the club still represents a mechanical marvel in the world of antique golf clubs and otherwise appears to be in outstanding condition.