The ubiquitous red valve. This amplifier pentode was a general workhorse. It was extensively used in radio and radar during WWII. This example was made in America but carries the pre CV VR designation of an RAF receiving valve.
The pins are equi-spaced around the circumference of the pin circle.
The Sylvania name and country of origin.
This valve was made as part of a contract for the UK Air Ministry.
The wide glass tube envelope is 34 mm in diameter, and excluding the B9G base pins is 61 mm tall.
References: Datasheet & 1040. Type VR91 was first introduced in 1938.