This Mullard 6V6GT/G was made in the USA. It carries the BVA logo and a code MLG. The 6V6/GT is in an etched panel of the type used by RCA.
The 6V6 family of beam tetrodes came in many constructions and were very popular as the final audio stage of broadcast receivers. The original 6V6 was an American metal can valve from the mid 1930s, and one of the first valves on an IO base.
The valves were capable of push pull use but the normal environment was as a single end output stage.
The etched identification.
The Printed label. Only the word Tested is now legible.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 70 mm tall.
References: Datasheet & 1040. Type 6V6GT/G was first introduced in 1937.