The CV3587 is an EHT power rectifier with a PIV rating of 35,000 Volts and a commercial equivalent of 705A.
The average rectified current is 100 mA with a peak of 500 mA. The construction is all glass with the lead-out wires being fixed to the main pins that are held in a ceramic disc outside the envelope. The special base clamps to this ceramic disc.
The anode fixes to the top pin and has three side wings for greater surface area and thus heat dissipation. The pins emerging from the base are then held firm in a ceramic ring that both guides the main pins into the base and provides a locating notch.
The Commercial Type designation of 705A and the maker's name Western Electric.
Looking into the cylinder formed from the three anode plates the filament can be seen as a helix with the return connection as a stout central wire.
The wide glass tube envelope is 57 mm in diameter, and excluding the B4A base pins is 119 mm tall.