The AU8 is a half wave EHT rectifier based on the Mazda U22 the AU designation indicates that it was made for the UK Army. The AU8 became the CV1356 with the arrival of the CV register in 1941.
The bright anode cylinder is connected to the top cap both electrically and mechanically
The spring attached to the anode is a tight fit to the envelope and adds to the mechanical rigidity of the anode.
The heavily insulated heater passing into the coated cathode tube.
The wide glass tube envelope is 28 mm in diameter and, excluding the MO base pins, is 79 mm tall.