Gang Green 68 GTS

I did find this -
"Gyro Matic Safety Control Devices - Anti Skid, Stabilzation | eBay"]Gyro Matic Safety Control Devices Anti Skid Stabilzation | eBay

It operates on the simple principle of physics - for every action, there is an equal and opposite reaction. When a skid occurs, the rear of the car moves sharply to one side. The Safety Control housing moves with it, but because of inertia, the weight inside stands still, compressing a spring on the opposite side. This causes a counter force movement of weight which tends to overcome the skidding movement of the car. The more violent the skid, the more pronounced the counter movement of the Safety Control device. Mounts with four bolts in the trunk in a position parallel to the rear axle. One device weighs 65 pounds. It's approx 26 inches long, 4 inches wide, 5 inches high.