The CV717 (5R4GY also on the glass) is a high voltage power rectifier and was designed for transmitter use. It has a rating of 180 Watts. The maximum reservoir capacitor is specified at 4 µF and the rectifier needs a series resistance of 250 Ω to limit peak current.
See also5R4WGY for a later version of this design.
The face of one anode has been ribbed for extra mechanical rigidity.
The top mica showing the fixings for the tops of the rods.
Under the top mica can be seen the tensioning springs and the hooks holding the tops of the inverted V coated ribbon filaments.
The classic envelope is 50 mm diameter, and excluding the IO base pins, is 115 mm tall.