The CV2218 is a HW power rectifier based on the VX7074. The commercial equivalent is the R17 and the special quality version is the 6157.
This rectifier has to be operated with a minimum of 50 Ohms of series resistance to limit the peak current. The maximum reservoir capacitor is given as 32 µF. The anode is taken to the top cap for additional isolation of the high voltage across the small envelope.
The side view does not easily show that the anode is essentially a pair of back-to-back U channels.
This image does reveal the anode profile. The central cylindrical space has wings that flatten out to make a large surface area. The blackening also aids heat dissipation by radiation.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 61 mm tall.