valve, tube, thermionic, electron, triode, tetrode, pentode, power,
magic eye, tuning indicator, nixie, history, data, data sheet,
specification, amplifier, radio, octal, B9A, B7G, B4, IO, KT88,
KT66, 12AX7, 12AY7, 12AT7, ECC81, ECC82, ECC83, 6L6, 6V6, EL34,
EL84, EM34, EM80, EM81, EM85, Mullard, Cossor, GEC, Gold Lion,
Marconi, Svetlana, Brimar, Ferranti, RCA, Sylvania, GE,
Mullard
This is a very early - 1925 or early 1926 - Mullard
PM series box. The boxes were made in various colourways. Note that
this one lacks any mention of the BVA and has a short list of
patents above the thinker.