The 813 is an RCA design. It is a high voltage, low current beam tetrode. This exhibit was made by Westinghouse in Canada.
The valve base would be mounted on spacers so that a blower could be fitted under the chassis and a stream of forced air cooling would pass over the envelope.
The anode seen side view, ie along the line of the grids.
The top ceramic insulator. The four side springs hold the electrodes in place within the envelope. The anode connects to the top cap in two places by a metal ribbon. In the centre are the two filament tension springs.
The classic envelope is 63 mm in diameter, and excluding the base pins is 165 mm tall.
Reference: Datasheet Type 813 was first introduced in 1954.