The T140 from Mullard is a high voltage half wave rectifier. It has been pumped to a very high vacuum without the use of a getter thus confirming the high voltage aspect. It is directly heated and the filament looks to be pure tungsten.
The Mullard logo. The anode connection is a large cylindrical structure but the anode is supported on a small diameter rod that will not conduct much heat.
The anode is shaped and made of sheet material rather than solid. This and the limited heat sink arrangement suggests high voltage but not high power. The filament is looped within the shield.
A standard X-Ray of the rectifier reveals the basic arrangement of electrodes.
Here the full detail of the inner structure becomes clear. The pinch and stranded wire connecting to the pins, the filament supports and the top pinch supporting the anode together with what appears to be a screw thread holding the anode external connection.
The wide glass tube envelope is 80 mm in diameter, and excluding the base pins is 240 mm tall.