The classic 807 beam tetrode from RCA.
The parameters given are for single ended use. When used in a class AB1 as a push pull pair with 600 Volts on the anode an output power of 65 Watts was normal.
The reverse with the RCA identification on the base.
The pinch, screen and lower end of the grids.
The anode connection to the top cap and the control grid heat radiator connected to the copper support rods.
The classic envelope is 51 mm in diameter, and excluding the UX5 base pins is 126 mm tall.
References: Data-sheet & 1040. Type 807 was first introduced in 1938. See also 1938 adverts.