The DE8LF is an AF amplifier and/or output triode depending on use. It is a dull emitter from 1925 and the all covering silver getting indicates that the oxide on the filament was made by the Azide process.
A little enhancement to reveal the Type designation and the type two BBC stamp that reads Entirely British Manufacture and was in use from September 1924 to 1927. The filament voltage of 5.6 Volts is also present.
The Osram Valve logo. Usually referred to as etched the lettering was probably made by a heat-set ink that is very difficult to remove. The base pins are of a two part construction - a central rod and an outside split sleeve.
The balloon envelope is 56 mm in diameter, and excluding the B4 base pins is 97 mm tall.
Reference: Data. Type DE8LF was first introduced in 1925. See also1925 adverts.
