Gold Seal Metal Tubes
|The Gold Seal
Manufacturing Company, of East Newark, NJ, introduced a line of strange
metal tubes in the early 1930's. They were actually glass tubes
inside metal shells, however.
The manufacturer touted the electrostatic and magnetic shielding that the metal shell supposedly provided, and the reduced space requirement. They were not inherently grounded through the socket, as were the shells of the later, true metal tubes. So, to be effective, an external method to ground the shell would have been needed, such as chassis-mounted contact fingers. This would have been a problem in replacement use in sets that already had tube shields. I know of no manufacturer that designed their radios to use these tubes.
These Gold Seal metal tubes had no impact on the tube market whatsoever, and quietly fell by the wayside as the giant corporations such as RCA and GE relentlessly pushed the technology forward. The heyday of the small, independent tube maker had passed by the early 30's, and the Depression made sure that very few would survive.