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.
The valves were capable of push pull use but the normal environment was as a single end output stage.
The classic envelope is 43 mm in diameter and, excluding the IO base pins, is 100 mm tall.
References: Datasheet, 1040 & 1043. Type 6V6G was first introduced in 1937.