Have any of you early Ford V-8 accessory guys ever seen or heard of "Robison Anti-Chatter Rings"? Made by Robison Air Jack Co, San Francisco CA, in the 1930's-40's. They were stampings, made to clamp around the outer edge of the brake drums, supposedly would reduce drum chatter. These were applicable to mechanical brakes only up to 1936. They were completely unlike the coiled spring-type appliances. Any info greatly appreciated. Thank You.