Moorhead designed and produced his R type to be used in place of the British R receiving valve. The R was made according to strict British specs and shipped to England.
The internal structure is vertical because Moorhead was supplied with only the specs and no drawing.
Moorhead also produced a transmitting tube called the B. Both of these valves were fashioned after the French type TM that had been designed in 1915 for the French military and then adapted to the British military standard.
The clear glass envelope does have markings but they are hard to see.
There are small white specs all over the glass. The filament is intact and the ripple will allow for expansion in length when hot.
The focus is on the lower part of the grid and filament.
The paper label around the brass base cap.
The etched identification on the bulb reads Moorhead San Francisco.
The filament is clamped in place by folding over the ends of the supports. The helical grid is supported by a single vertical strut. Likewise the anode is held in place by a single support that is anchored in the glass pinch.
A closer view of the electrodes and the pinch.
An enhanced monochrome view of this historic valve.
The feint number on the glass reads 40548.
The balloon envelope is 54 mm in diameter and, excluding the B4 base pins, is 97 mm tall.
Reference: Joe Gruber. Type R Type was first introduced in 1916. See also1916 adverts.
