[Brad Winder]

As Arran mentioned, Philco would use a tube (or tubes) that they got a deal on, and design circuits around them. Quite often the tubes were "obsolete" compared to what other manufacturers were using at the time. But I guess you could also look at the tubes they used as being "proven" by being around for several years prior. And their sets were very good performers, so you can't say they cheaped out.

I find their early 40's sets most interesting in this regard; using a mix of Loctal, which was a brand new design, with five and six pin ST tubes, plus still using an 80 rectifier, while other manufacturers had switched to the 5Y4, etc.