The PHILCO Phorum

Were loctal tubes used for a long time? I mean if you come across a device using 7F7s and 7N7s could you guess that it might be more likely to be from a certain decade?

Mostly you see loctals from the early to late 40's, not a lot were used in the late 30's that I can recall and they were used I think into the early 50's.

Philco began wide use of loctal tubes in its 1940 models, and continued to use them for a few years after World War II.