Tube Factory Codes

111 = Amperex
158, 171 = DuMont
188-... = General Electric
210 = CBS Hytron
247 = National Union
260 = Philco
274 = RCA
280 = Raytheon
312 = Sylvania
322 = Tung-Sol USA (Beware for new production Tung Sol, this is not made by Tungsol, but by Russian "Reflektor" factory)
323 = United Electronics
336 = Western Electric
337 = Westinghouse
722 = Sylvania-manufactured for OEM equipment makers
1022 = Fisher branded Mullard/Telefunken/Amperex
1109 = Raytheon, Japan
Xf1, Xf2, Xf3, Xf4 = Mullard
7C,8I = Toshiba