This is a version of the British 'R' valve (tube), made for the British Army during WWI by the U.S. company Moorhead. One noticeable difference between this version and the European 'R' valves is that the anode (plate) structure is mounted vertically rather that the more usual horizontal arrangement. This appears, amazingly, to be due to the fact that the company had not been supplied with details of the mounting arrangement. The pure tungsten filament was designed to run at 4V, 0.7A nom.
Over 20,00 of these tubes were supplied by Moorhead to British forces during WWI. The envelope of above example is marked in gold lettering as follows:
The number 40680 is the serial number. The text just above the serial number is not all that clear but may read SEATTLE R(A) .
The paper band around the brass base reads:
This Moorhead valve is licensed
under the Fleming patent-Number 803684. Other patents pending.
Copyright Ó 2003 Lorne Clark