This exhibit has no markings or identification. Comparison with CV172 suggests the same electrode configuration and possibly the same functionality. That would make this valve a noise diode, a source of white noise.
White noise is used in response testing and as the start point for wide band noise to use in a jamming transmitter.
The lower part of the envelope contains a box anode running horizontally above the pressed glass base disc. Threaded through this is a V of filament, all three points of the V are brought out to pins. Above the anode appears to be a getter that is also connected to a base pin. The latter connection to the base may be purely for support, but it may have a purpose.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
Updated March 01, 2013.