The TY4-500 is a VHF power triode with an anode dissipation of 450 Watts and designed for use at full ratings at up to 120 MHz. It is directly heated with a thoriated tungsten filament.
The TY4-500 would be used within AM transmitters and often the modulator was the same type of valve. For a pair of TY4-500s operating as a Class B modulator with 4kV on the anodes an output power of 2.1 kW was possible.
The valve is branded as Mullard but was made by the parent company Philips in Holland.
The graphite anode is ridged to increase the surface area available to radiate away the heat generated. The envelope would also need to be cooled by air passing over it.
The five pin base. The two lower pins are the filament and the other three are the grid connections. The anode, of course, connects to the top cap.
The wide glass tube envelope is 115 mm in diameter, and excluding the base pins is 180 mm tall.
Reference: Datasheet. Type TY4-500 was first introduced in 1957.