The VR37 (from 1941 the CV1037) is an indirectly heated triode based on the M-OV MH4.
The VR stands for Valve, Radio and was the RAF designation. Here the Crown and AM for Air Ministry is printed with the testing side in the circle below.
The anode seen full face.
The side view shows the anode to be 5 mm front to back.
The cathode tube is held at the top by two supports that are fixed to the horizontal bar. The shaped control grid can be seen through the gap between the top mica and the anode as can the white face of the rectangular cathode.
The balloon envelope is 45 mm in diameter and, excluding the B5 base pins, is 96 mm tall.
