The CV395 is a voltage stabiliser tube that operates with currents through the valve of between 5 and 45 mA and maintains a voltage of 150 Volts. The prototype was the VX372. a(a) is a priming anode. The commercial version is the G180/2M from STC
The English Electric logo and name, plus Made in England. On the base skirt is the locating pip for the B8B or Loctal base.
The outer electrode is continuous and obscures the inner rod.
The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 63 mm tall.
References: Datasheet. Type CV395 was first introduced in 1950.