The V20 is a half wave indirectly heated rectifier designed for 200 mA series connected heaters as found in AC/DC radio receivers.
Face view of the anode. The anode occupies most of the envelope so as to dissipate as much heat as possible. Other similar rectifiers have smaller anode surface areas and probably ran much hotter.
The B5 base and pins.
Thanks to Mark Mallison for sending the images.
The wide glass tube envelope is mm in diameter and excluding the B5 base pins, is mm tall.
References: Data &1043. Type V20 was first introduced in 1937. See also1937 adverts.
