The CV78 is a transmitting triode with an anode dissipation of 8 Watts and an intended operating frequency up to 600 MHz. It was designed for use in a grounded anode configuration.
The electrodes are mounted horizontally with two side flanges providing for the required heat sinking.
The GEC logo. M-OV labeled devices for professional use with the GEC brand.
Looking into the glass the box anode can be seen. Inside the anode the control grid, wound on copper supports, passes flat across the wide cathode.
The wide glass tube envelope is 32 mm in diameter, and excluding the base B9G pins is 56 mm tall.