The VR109 (CV1109) is a triode known also as the NR55, AR7, during 1941 renamed the CV1109. This exhibit was made for the RAF before 1941.
The prototype was the 4D1.
The crown and AM of the Air Ministry.
NAPL has to be a depot or test area. The triode stands above the pinch and the control grid connects to the top cap
The heater can be seen to pass multiple times through the cathode tube. The internal working part of the anode is cylindrical.
Although the envelope is shouldered to allow for an interference fit of the top mica, here the top mica does not make contact with the glass. All the support is from the pinch.
The classic envelope is 38 mm in diameter and, excluding the B7 base pins, is 97 mm tall.
Reference: Data-sheet. Type VR109 was first introduced in 1934. See also1934 adverts.
