The 6K8G is the classic triode hexode frequency changer or mixer for broadcast applications. The exhibit has a clear glass bulb and would rely on external shielding where other mixers had external zinc paint sprayed on to provide screening. For isolation of the signal input and output circuits the hexode signal grid is taken to the top cap.
Unlike 6K8G from Brimar this exhibit has a perforated screen almost identical to the Tungsram 6K8G.
The electrodes from the other side of the envelope.
The pinch and lower mica: the heater and cathode are offset from the centre.
A closer view of the perforated screen. The inner structure is not clear. A diagram of the construction can be found in 6K8.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 101 mm tall.
References: Data-sheet & 1040. Type 6K8G was first introduced in 1938.