While we are on the subject balancing stuff; you may be interested in seeing the machines that are used these days. Micro Poise (MP) Balance Engineering Co. Troy MI.
Back when I worked for GM , Cadillac in the 60's and 70's we used propriety balancing machines manufactured by General Motors, There was a small division "GM Balance Engineering". I believe that there is a historic connection to MP Balance Engineering.
https://www.machinetools.com/en/comp...neering/models
Joe B