The PCL83 is a television audio triode output pentode from the era of VHF television in the 1950s. It produces enough output power for an average domestic environment but was designed for frame timebase and frame output.
This standard design was made by several manufacturers. This exhibit has the later Mullard logo.
This view is looking directly into the anode of the triode.
The two electrode systems are mounted side by side and this image is along the axis of the grids. The pentode has the screen grid and the outer suppressor grid visible through the end wall of the anode.
The pentode anode.
The thin glass tube envelope is 20 mm in diameter and excluding the B9A base pins, is 47 mm tall.
References: Data-sheet & 1040. Type PCL83 was first introduced in 1954.