The 8019 transmitting triode has a directly heated thoriated tungsten filament and has the electrodes sealed into a glass pinch and is fitted with a B4 base. It is also probable that the RCA type 834, with the UX4 base is a direct electrical equivalent.
The M-OV type DET12 of 1936/7 is either the original design or was influenced by the RCA design. The first DET12's had a carbon block anode.
The anode can dissipate 50 Watts. Both anode and control grid have connecting pins at the top of the envelope and thus minimise the inter electrode interaction.
This exhibit is marked for Royal Air Force use (VT prefix), the Navy also had a version of the valve and when the Common Valve designations appeared the valve was still in use. In addition to the VT62 the base has the old stores code of 10E/11443.
The anode held by the top pin only and likewise the control grid is only held from the top.
The grid seen from below is a rhombus. The helical filament is in the centre of the anode.
The balloon envelope is 66 mm in diameter and, excluding the B4 base pins, is 151 mm tall.