This exhibit is an R Type receiving valve made by the Penton Engineering company. Penton were active from 1924 to 1926 and this valve carries the type one BBC stamp that was in use from November 1922 to September 1924. Thus this valve is one of the first valves produced by Penton.
The anode is helical wire rather than a cylinder and this may have been to bypass the existing patents.
The base cap is chrome plated brass and the electrodes are held in a fan shaped pinch.
Here the concentric structure is clearly visible as is the tungsten filament. Although broken, the wire can be seen to have been a loose helix. Filament fixing is mechanical in the fold of the supports. Also visible is corrosion to the supports. The valve looks to be air-tight but probably the vacuum has long since gone.
The concentric structures. Each of the three electrodes is supported at both ends.
The makers name and Type designation are etched into the glass.
The type one BBC stamp has been etched into the glass opposite the Type designation.
The balloon envelope is 59 mm in diameter and, excluding the B4 base pins, is 113 mm tall.
References: 1003. Type R Type was first introduced in 1916.