The Lissen SG215 tetrode was introduced in 1929 with a screw top cap. It is a screen grid or tetrode valve for RF amplification in battery operated broadcast receivers.
It was made in both clear - for using an external screening can - and metallised versions - integral screening.
The identification printed on the glass and reflected from the silver gettering on the inner wall of the envelope.
The flat mesh is one of the anode plates. The screen grid winding has flat sides. The control grid is wound round two supports and within in can be seen the filament - a single V.
The balloon envelope is 41 mm in diameter and, excluding the B4 base pins, is 119 mm tall.
Reference: Data. Type SG215 was first introduced in 1928. See also1928 adverts.
