The VR109 is a triode. The VR indicates an RAF specification. The same valve was also specified by the Army as the AR7 and the Admiralty as the NR55. During 1941 the UK Government standardised on Common Valve specifications and the Type became the CV1109.
The prototype was the 4D1.
The old stores code for the VR109 was 10E/11098 as can be seen on VR109. Here the code is 10A/11098. We can find no reason for this as yet.
The crown and AM for Air Ministry.
The code in the circle is 101 but the word round the circumference is Brimar - the STC brand.
The anode and top mica. The wire extensions grip the inside of the glass.
The classic envelope is 37 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.