Strange Telefunken tubes
May I offer (with the help of Emilio Ciardello and Alessandro dePoi) a theory to explain the phenomenon of Telefunken RENS324, RENS351, RES347, RGN380, which are similar to the US-types 24, 35/51, 47, 80. Not enough with similarity of data and bases, looking at the bulb shape it is clearly not Telefunken-like. It is rather a Radiotron clone. The radio where such tubes are employed is an Italian Telefunken 540.
Italian subsidiaries of foreign companies like Siemens, Philips, Marconi and also Telefunken operated with relative independence from their parent companies. They had to demonstrate that they were selling more and more Italian made goods and sometimes used a lot of tricks to reach their target.
May be that Telefunken just bought some lots of US unmarked tubes and put their own logo and codes on them. No wonder, because unmarked or unbased tubes were considered raw material. The printing of a code upon them or a rebasing could justify a "production" with subsequent financing by government. Of course, no trace could have been left in the documentation of such tricks.
Another possibility is an RCA licensed production by Fivre for Telefunken.
Not to forget the mutual Patent Exchange Agreement RCA-Telefunken of 1920.
But it is still a theory...