100TH transmitter triode

An old convection-cooled transmitter triode, with 100 W max. anode dissipation. Grid connection is at the side of the bulb, plate at top, the socket only supporting the filament leads. Filament (thoriated tungsten) rating is 5 V at 5 A (?).

Plate is made of hard metal with an external high-temperature getter coating. This tube is part of a series of transmitting triodes, another well-known type being the 250 TH. Similar to these high-mu types, there were low-mu parallel types, like the 100 TL, 250 TL, etc. The tube shown in the photo is made by Lewis and Kaufman Inc., USA.

A bit different, though in similar bulb shape, is the type 304 TH/TL. It is made of 4 identical systems (4 filaments, 4 grids, graphite anode block with 4 system cavities) arranged in parallel. 

These tubes were used mainly in amateur transmitters as finals, or in larger stations for modulator service. No. 304 was also used for pulse applications.