The 100T (Lo) is the re-designed and uprated 50T triode made by EIMAC. It was then re-rated to 100 watts. The 100Ts are marked on their filament stems with Hi (30) and Lo (12) to indicate the mu. At first the tubes were just called the 100T and the Hi or Lo version, but later advertisements adopted the names 100TH and 100TL. Other tubes such as the 250T also used this convention and these were problems with customers being confused. New tubes with the new names, 100TH and 100TL, replaced the old versions. The mu of these new tubes was different than the early tubes. The first example is a typical "Hi" tube with its open anode top, 3 wire plate wire seal and 3-way grid support. The second example is a "Lo" with the closed plate structure of the later 100TH/TL tubes while retaining the 3-way grid support. The last example is a "Hi" tube and has the same grid support and anode and is identical to the later 100TH.
Length = 7.75" Diameter = 3.19"
Max voltage = 3000
Max current = 225 ma
Fil voltage = 5
Fil current = 6.3 amps