The CV1823 (Commercially the 1N5GT) is a variable μ RF pentode for dry battery operation. The original design came from America but the CV specification would indicate specific requirements of the UK Government if they differed.
This exhibit has the later composition base. Our other example has a metal skirt around the inner plastic base.
The filament is a single vertical strand. The top connection to the filament has a tension spring with the filament clamped in a small length of tube.
The CV1823 is used at both RF and IF in superhet receivers.
The /T identifies the maker as British Tungsram, Tottenham.
The mesh screen hides the inner electrodes.
Looking through the gap between the perforated screen and the base screening disc the grid windings can be seen. A single thin wire of the suppressor grid is visible. The inner grids are curved around the filament.
The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins is 77 mm tall.
