The PC900 is a miniature VHF amplifier triode for use as an RF amplifier in television receivers. It is low impedance and has a high mutual conductance. This is partly achieved by a very low cathode to grid spacing. The anode is made of two rectangular channels, one either side of the cathode. The beam plates form the electrons into two beams.
The anode is shaped so as to give sufficient area to dissipate heat but also to present just a small flat area to the electron flow. The anode looks to be made in two pieces but is a single pressing with a strap connecting the two sides. The anode is mounted either side of the central cathode and frame grid.
This image shows that the mass of anode metal is to the outside with a small part close to the cathode.
Made in Great Britain.
Here the fine grid winding can be seen.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 32 mm tall.
References: Datasheet, 3002 & 1040. Type PC900 was first introduced in 1963.