EB91 first availability
There seems to be quite some confusion about the first availability of the EB91 valve, where the official date of launch is quoted as 1949. However, to me it has now irrevocably been confirmed that the valve was available in 1946 in the UK.
My interpretation is the following. The EB91 was developed by Mullard, the British subsidiary of Philips. Proof to this is that the valve was used in three TV sets developed by Mullard/Philips in 1946: 463A, 563A and 663A. These were demonstrated at the 1947 Radiolympia show in London, and commercially launched the same year. The valve was also sold to the UK set maker Pye, who launched two sets in 1946, the B16T and D16T. They were announced in the December 1946 Wireless World and produced in 1947.
All in all the valve was probably released end of 1945, used for development in 1946 and ramped in production in 1947, all in the UK only. After that it was most likely taken over by the larger Philips Radiobuizen (Radio Valves) Group, standardized and launched Europe-wide in 1949.
Please read post 5 here - to have the possible answer.