The RT323 is a Japanese power tetrode developed and used in WWII as a Radar transmitter valve. It was used in the 'Ta-Chi 7' Type B mobile early warning device. This ground based Radar operated at 100 MHz and was developed in 1943. It is believed that about 60 of these Radar sets were made.
The base is a special four pin type. The copper anode is coupled to aluminium radiating fins and the valve is very light.
Thanks to Ken Yamamoto for sending details of this valve.
The envelope is 67 mm in diameter and, tip to tip is 165 mm. The anode fins are 90 mm in diameter.
References: Ken Yamamoto.
Updated December05, 2012.