It was not uncommon to mount radio chassis on springs or rubber washers to reduce microphonics.
My Zenith 12-S-471 radio had spring mounts on the chassis; tapping certain tubes would give you a brief chime, but it never grew into a squeal. My Stewart Warner 1865 radio is mounted on rubber washers. My Philco 42-1240 TV is mounted on rubber "feet," presumably for the same reason. The Philco feet were used on various TV chassis, commonly enough that someone now makes repros.
If microphonics are a serious problem with your TRK-12 radio, you could try adding damper rings. You'll find lots of info about them in an Internet search, and not all of the info is snake oil. The lead damper on my T-100 tube was there for a reason.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html