The VR65 is a WWII military receiving pentode valve made for the RAF. The VR in the designation provides this information. Commercially this is an SP61 that was developed originally for television RF stages. The SP41 is the same electrically but has the pre-war 4.0 Volt standard heater.
With the grid at the top cap, this is the normal pattern for RF and IF amplifier valves of the period. Providing high gain in tuned anode circuit applications. For additional screening the valve was originally covered with an external metallisation that has since fallen off revealing the construction..
The VR65 was used in air-borne radar particularly GEE.
A true pentode with three wire grids the anode consists of two small plates joined by a strap - seen at the left. The speckles on the glass come from the adhesive used to hold the metal loaded coating in place.
Looking along the grid axis with the anode joining strap in the foreground. The flat face of the rectangular cathode allows the dark lines of the control grid to be more visible.
The classic envelope is 32 mm in diameter and, excluding the MO base pins, is 82 mm tall.
References: Data-sheet & 1043. Type VR65 was first introduced in 1941. See also1941 adverts.
