Thanks for the information! I had no idea Rogers was so heavily involved in radio and tube development, not to mention broadcasting.They even had an experimental FM station (VE9AK) prior to WWII.
Did Rogers make any spray-shield tubes in the pre-octal base configuration, which would have been before 1935?
If they did, then I’m sure they invented the process and Grigsby-Grunow just went along for the ride.
GG was not noted for innovation in the tube making business. In their own plant and the LaSalle facility they later bought, they mostly manufactured tubes designed by others.
I’m pretty sure the “merger” between Rogers and Grigsby-Grunow, mentioned in a couple articles you cited, was not much more than a cross-licensing agreement, as Rogers did not go down the tubes when GG did in 1933-34.
One of my U.S. sources — I think it was Antique Radio Classified in a history of Majestic radios — said Rogers made two separate lines of radios in the late 1920’s — one under the Rogers name and one under Majestic (NOT Rogers Majestic). The author said the main difference between the two lines was cabinet design. The innards of both supposedly were Grigsby-Grunow. This sounds unlikely to me.