UB41

It is stated that the UB41 (and the associated EB41) were only released in 1950. This is not correct.

These tubes came available early 1948, at least for internal development within Philips. There are circuit diagrams from July 1948 (for a 567-line television design) using the UB41, while the TF384A television designed early 1948 used the UB41 too (the 8 in the name indicates it being a 1948-released design). The Philips Radiobuizen Lab had television reference designs using the EB41 and dated August 1948. Both these Rimlock valves were publicly announced in a Philips Electronic Application Bulletin of December 1948.

Especially the UB41 was used in Philips television receivers from 1948 and 1949: the TF384A, TF390A, TF402A and TF502A for the French market, the 385U, 485U, 683U and 492U for the UK market. The EB41 was used in 1950 in the TF651A, TF751A and successors until 1952.

Please read post 5 here - to have the possible answer.