The UK Army receiving valve AR was made with the I/S4 and I/S3 inter-service base. The AR3 seen here is fitted with an I/S2 base. The AR series had the 2.0 Volt 0.4 Amp filament rating. These are dull emitter valves with a thoriated tungsten wire as the emitting surface.
The handle indicates that it was pushed into the socket horizontally.
The triode anode is a small diameter cylinder.
The AR3 designation with 2.0V underneath.
The base indicates the anode and grid connections with the filament connected to the base studs.
The helical grid is welded to a single support rod. The filament (broken) is a single vertical thread.
The top of the anode with the filament tension spring on the left. The thin spring is welded to th side support rod.
The lower end of the filament is all that remains.
The base is 36 x 29 mm. Side contacts excluded.
The thin glass tube envelope is 26 mm in diameter, and excluding the I/S2 base pins is 82 mm tall.