Best 6F6G pairs listed at:

6F6=VT-66 / 6F6G / 6F6GT Pentode
6F6=VT-66 Metal Can (US BRANDS) (similar to Type 42 and 1611, 1613, 1621) (6.3V @ 700ma, 11 watts) - Sparton Nocturne 1186 from 1936 - Fire Stone Sir Chef S-7404-3 1939 - Montgomery-Ward Airline Model 62-226 TO BUY 6F6 metal can

6F6G US Brands / CANADA / FRANCE (similiar to 10E/346, KT63, VT-66A, CV1911) TO BUY 6F6G
- Supratek Cortese - Victoria - WE 106 preamp clone - Wards Airline Radio
6F6GT (very nice in Supratek Cortese) 6F6GT Sylvania branded Philco and Westinghouse 1951-1952 TO BUY 6F6GT