The 6V6 family of beam tetrodes came in many constructions and were very popular as the final audio stage of broadcast receivers. We have the original American metal valve 6V6 produced in the mid 1930s and subsequently used for military designs and a miniature glass tubular version the 6V6GT. The 6V6 shown here is of the large glass type and the inside of the envelope has a grey smoked finish.
The base also carries the old UK military stores code of 10E/349.
The valves were capable of push pull use but the normal environment was as a single end output stage.
In this 6V6G the internal coating is not opaque. The anode is oval and the control grid is wound on copper supports and has a heat sink above the top mica.
The lower part of the anode and the electrodes. The indirectly heated cathode in the centre with the copper grid supports clearly visible. The beam plates are in the same plane as the screen grid in this image.
The classic envelope has a maximum diameter of 43 mm and a length excluding the IO base pins of 97 mm.
References: Datasheet, 1040 & 1043. Type 6V6G was first introduced in 1937.