Fig. 1 above has the usual Post Master General markings, R valve and the words “Made by the MO Valve Company”, GEC, made in England. However, there is no mention of the patent status. Considering the plain box that only states R, it may seem that this group of tubes were the first to be sent for war use. It does have a slight golden tint to the bulb. There is inked wording on this box that cannot be read but probably has the same wording that can be seen etched on the bulb.

Fig. 2 has the same Postal etchings , R valve with the added Marconi/Osram logo and the words “Lamp Works”, and now with covered by “Various Patents”. The box states Hammersmith which is the town in which they were made but no mention of GEC. Now the bulb has a phosphorus getter.

The fig. 3 valve has no Post Master General markings but has R, Osram GEC, and made in England. No patent numbers at all. The box is quite plain but has the words “Valve, WT, and Type R” inked. This may be another early production for WW1 and post WW1.

Fig. 4 above has the usual Post Master General logo, Marconi/Osram logo but now with “covered by various patents” wording as in fig. 2. The bulb shape has changed along with the phorphorus getter.

Keith throwers book sheds very little light on the subject but examples are not easy to find for comparison.

Leave a message with your thoughts and possible new information.