The AR is a bright emitter receiving triode. The AR stands for Amateur Radio. The AR design originated in 1922 and was a development of the R Type, the μ was given as 10. Ediswan were among the first manufacturers of the R Type in Britain and the AR shows the way that valve technology developed. The anode became a vertical cylinder and the filament became supported on a sprung support to maintain filament tension when hot. The move to a vertical anode is interesting as the original TM valve used a horizontal anode to remove the original problems of the vertical anode.
The first version of the BBC Stamp. This dates this valve to between November 1922 and September 1924. All pins are full length and Ediswan introduced shorter filament pins during 1923.
The single anode support is on the left.
The single strand tungsten filament is intact. The grid is supported between two support rods and fixed with thin wire. The anode support is substantial as are the grid supports.
The wide glass tube envelope is 28 mm in diameter, and excluding the B4 base pins is 86 mm tall.
References: 1004 & 1003. Type AR was first introduced in 1922.