The PCL805 triode pentode was purpose designed as a domestic television receiver frame output stage for monochrome sets and on rare occasions (ITT CVC5 chassis) colour sets. As is common with TV valves it is designed to operate at a relatively low voltage and high current. The beam tetrode has a quoted load resistance of 4,000 Ohms.
The literature gives ratings for audio service but the PCL86 was the normal audio stage valve.
The third grid is the bright plate seen through the holes in the anode. This is a beam tetrode. The grid fins connect to the screen grid.
The small triode is seen on the left.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A pins is 69 mm tall.
References: Datasheet & 3002. Type PCL805 was first introduced in 1968.