The Cossor New Process 220HPT is a battery audio output pentode.
The load resistance is 10,000 Ohms and this is greater than high impedance headphones, so clearly this valve would have been used with an output transformer to transform the impedance to that required by a loudspeaker.
The top view shows the wire grids within the bright anode. The left hand coated filament has broken and is displaced to the left.
Top dead centre showing the shapes of the mica supports and the distance between the electrodes and the outer wall of the glass envelope.
The balloon envelope is 45 mm in diameter and, excluding the B5 base pins, is 92 mm tall.
References: Data-sheet & 1043. Type 220HPT was first introduced in 1932. See also1932 adverts.
