I see lots of "who made this tube?" or "I don't know who made these..." posts. While manufacturers made tubes for each other all the time, it's often easy to figure out who made a particular tube. GE's markings are very distinctive, but several manufacturers (most notably Tung-Sol) used an octagon very much like RCAs. In these cases, there's usually a three-digit number printed with the markings. (In some more rare instances, it's a four-digit code)
Amperex (US production) = 111
GE = 188
CBS/Hytron = 210
RCA = 274
Raytheon = 280
Sylvania = 312
Tung-Sol = 322
Western Electric = 336
Westinghouse = 337
If you find something odd, usually a quick Google search will turn up who that EIA code belongs to. Here's one page that's a good reference: http://www.triodeel.com/eiacode.htm
The codes aren't always present, but when they are, there's no need to wonder who made your tube!
Amperex (US production) = 111
GE = 188
CBS/Hytron = 210
RCA = 274
Raytheon = 280
Sylvania = 312
Tung-Sol = 322
Western Electric = 336
Westinghouse = 337
If you find something odd, usually a quick Google search will turn up who that EIA code belongs to. Here's one page that's a good reference: http://www.triodeel.com/eiacode.htm
The codes aren't always present, but when they are, there's no need to wonder who made your tube!
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