[RadioSvit]

Mike;
From what I have read elsewhere those short metal tubes where called "stahl" or steel tubes, and were developed, and originally produced by Telefunken in 1938. The first time I saw some was in a war time set another collector had, they looked like oversized 6H6 tubes, and from what I can tell they carried on making them in Germany, and Poland well into the 1950s (or later), maybe some other Warsaw pact countries as well. Do they all have eight pin bases in that set? A really strange pinout, five on one side and three on the other, I would guess that the three pin side is for the tube heater plus the cathode, but since the base has a key why bother?

Arran, this type of German radio lamps has another slang name - "helmets". From the extraordinary similarity with the German helmets of the Second World War. And you would probably be very surprised if you saw the structure of the armature of these radio lamps - it is not placed vertically, but horizontally. That is, the filament, cathode, grid and anode are in a horizontal position, not in a vertical position! As it was in radio lamps at the beginning of the 20s