Nuvistor

The nuvistor is a type of vacuum tube developed by RCA in the 1960s. Most nuvistors are basically thimble shaped, but somewhat smaller than a thimble. Triodes and tetrodes were made, although tetrode nuvistors are rare. The tube is made entirely of metal and ceramic.

Nuvistors are among the highest performing small signal receiving tubes. They are very noise-free, for a tube. They feature excellent VHF and UHF performance. They competed with the solid state revolution, and along with GE's Compactron, probably held it at bay for a few years.

Example Nuvistor types:

7586 - First one released, medium mu triode.
7587 - Sharp cutoff tetrode.
8056 - triode for low plate voltages.
8058 - triode, plate cap & grid on shell, for UHF performance.
7895 - 7586 with higher mu.
6CW4 - high mu triode, most common one in televisions.
6DS4 - remote cutoff 6CW4.
6DV4 - medium mu, intended as UHF oscillator, shell sometimes gold plated.