Stewart Warner Radio Vacuum Tube microphonic Dampers Zinc HEAT SHIELD RARE

I was told these were used to minimize microphonics in the tubes, microphonic sound like ringing in the chassis, or even the cabinet, if tapped or knocked on

They went over vacuum tubes to reduce vibration and protect against heat hence they are heavy and thick and made of ZINC

EITHER WAY YOU COLLECTORS WILL KNOW WHAT YOUR LOOKING AT