The Type 45 is a directly heated audio output triode. This exhibit is from a late production run and is housed in a classic envelope. See also45 for the original balloon production.
The Tung-Sol name and by the side of the anode are the filament tension spring supports.
Face view of the anode. The filament can be seen as an M shape and the wire is oxide coated, the grid wires extend below the anode.
This top view shows the support mica, tension springs and the spacing between the three electrodes.
The classic envelope is 44 mm in diameter, and excluding the UX4 base pins is 98 mm tall.
References: Data-sheet & 3002. Type 45 was first introduced in 1929. See also1929 adverts.