The A2913 is a special quality low noise VHF amplifier triode. The anode dissipation is 2.5 Watts and the grid is of frame-grid construction. Lower noise figures were obtained by running at higher anode currents than one would expect for a small signal RF amplifier.
The A2688 or CV4081 is the same valve but fitted with a B7G/F or wire base.
The GEC paper logo.
The anode us a flat top U shape channel. The grid is wound on a flat former with wide side pieces. The frame-grid is wound at about half of the breaking strain of the fine wire used.
The thin glass tube envelope is 17 mm in diameter, and excluding the B7G base pins is 35 mm tall.
References: Datasheet & 3002. Type A2913 was first introduced in 1940.