Count on Stromberg-Carlson to use parts well past their prime (just like their design style...). AR-37 amp used push-pull 6F6s (1952 Sams folder, possibly earlier). Also the AR-410 amp (1953). And the SR-405 mono receiver used 6F6s (1954). Sams folders and other information are on my Stromberg page:
http://www.audiophool.cjb.net/MadeInRoch.html