The 250T replaced the 150T triode by 1935. It was then rated at 250 watts. The 250T came in two types. One with a high mu (32) and a second with a low mu (13). A "HI" or "LO" was printed on the filament stem. It is usable up to 40 MHz at full rating. The single filament lead press is typical, but early tubes like the first example, had the 3-way grid support as found in the 150T. Both examples are "HI" versions. Late production of this tube was called a 250TH or 250TL in data sheets.
Length = 10.13" Diameter = 3.81"
Max voltage = 3000
Max current = 350 ma
Fil voltage = 5
Fil current = 10.5 amps