[Tubesforme]

Prior to 1930, there were no Philco branded tubes.

I have a 1929 ad somewhere with Walter Holland, Philco's Chief Enginner at the time, extolling the virtues of RCA Radiotrons.

In 1930, by which time relations between RCA and Philco had taken a turn for the worse, Philco made a deal with Hygrade and Sylvania to supply tubes instead of RCA. The deal was sweetened by Hygrade and Sylvania agreeing to put Philco's name on the tubes.

I have a sheet with the 1930-1934 date codes somewhere. I just don't know where right now. That code used twelve letters which stood for the twelve months of the year.

Around 1935 or so, Philco (Sylvania) switched to a simpler date code - O P U S - in which 5O (or O5) stood for first quarter, 1935; P5 = second quarter 1935; U5 = third quarter 1935; S5 = fourth quarter 1935.

Thanks Ron, I hope that you come across the sheet at some time. I always follow the Phorum and so if it is posted on the Phorum, I will see it. You have a great and very helpful site here.