This exhibit is a Moorhead B fitted with a British B4 base cap and made for the UK Government. For the development samples the B was fitted with the American Shaw Base (See the PDF below).
Both the Moorhead R and B exceeded British Army expectations and were very well regarded.
The B had a low vacuum for use as a detector. The anode voltage range was 18 - 40 Volts.
The valve has phosphorus gettering and the design dates to 1916.
The serial number is 6255.
The paper strip gives the Moorhead name and details of the patents used.
The orange gettering masks the internal structure. The construction is of a horizontal cylindrical anode, a helical control grid with a single side support and a single strand filament running along the centre.
The grid support wires are twisted together to form the lead reaching to the pinch. The twisted wire would be more mechanically stable that the individual wires.
The anode cylinder is rolled with the ends just meeting but not fixed together.
The geometry showing the relative dimensions and positions.
The balloon envelope is 54 mm in diameter and, excluding the UV base pins, is 92 mm tall.
