The AR.06 is a dull emitter triode that was introduced in 1923. This exhibit is the general purpose variant, the original. Two other variants were also made and introduced in 1925: red line - for RF and detector use and green line for detector and AF.
The AR.06 was one of the first dull emitter valves from Ediswan, the other was the ARDE also introduced in 1923. Both of these valves had thoriated tungsten filaments. The bright emitter AR was still made when broadcasting commenced.
The base on the AR.06 has the metal shell surround but the safety cap, with the short pin, was not present.
The anode cylinder is mounted vertically. This image shows the grid and also reveals that the filament has failed.
The high tech nature of the valve in the 1920's can be seen by the way the valves were protected in transit. The box is made from substantial cardboard and has an inner liner. The padding was made from horse hair and the box top is equally well designed and protected. The bright colour and operating details printed on the box testify to the fact that the user was probably also a set builder and buyer of the actual components.
The wide glass tube envelope is 29 mm in diameter, and excluding the B4 base pins is 92 mm tall.
References: 1003 & 1004. Type AR.06 was first introduced in 1923.