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.
Another example with yellow lettering. The anode is formed as flat plates in the direction of wanted electron flow and reduced to small straps at right angles to the working direction.
The anode is formed as a pair of boxes either side of the grid. The latter is made of very fine wire and this wire passes flat across the cathode. It is probably a frame grid, with the wire wound under significant tension.
The anode face on. The lettering says that this was made in Great Britain.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 32 mm tall.
References: Datasheet, 3002 & 1040. Type PC900 was first introduced in 1963.