RCA released the first 7 pin "button base" tubes in 1939, consisting of four 1.4V filament types, later followed in 1941 by the first three 6.3V indirectly heated types, the 9001 9002 9003. Then 6C4, 6J6, 6AK5 in 1942, and in 1945 by the very common AM radio types 6BA6, 6BE6, 6AT6, 6AQ5, 6X4.
Britain, Germany and Holland did not produce RCA's "button base" types until 1947, mainly due to the war time conditions in Europe 1939-1945.
RCA released the first 9 pin "button base" tubes in 1948, the 12AU7 & 12AX7.
(Ref. "70 years of radio tubes and valves", John W Stokes, 2nd ed, p135-140