Mfr radio dating
and so on, Sylvania, RCA, Tung-Sol and everyone else at some time relabeled tubes!
This is why we have to LOOK AT THE ORIGINAL FACTORY CODES IF PRESENT (NOT THE UNITED ELECTRONICS RELABEL CODE),, and identify the real tube manufacturer by codes, inner construction, shape of the tip, and shape of the getter ring to determine the real origin of the tubes. J., USA) was a company that simply re-labeled Tung-Sol, RCA, Sylvania, and GE USA made tubes for resale.
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When a government requirement for CV4017 tube specification came in a Request For Proposal (RFP) to the 4 major USA tube factories they all worked together to source from one another to fill the orders.
This is why we see so many tubes made by Tung-Sol labeled as RCA, RCA made tubes labeled Sylvania, Sylvania made tubes labeled GE ...
5 is the plant code (in this case, Owensboro, Kentucky). And another is like this: 322 6104-1 322 is Tungsol, 6104 is 1961, 4th week, 1 is the shift code (1 would probably be the day shift) After about 1960, many tube manufacturers went to encrypted alphabetical date codes., such as: KE 188-5 The reason was purportedly to allow factories to track the dates of manufacture of defective tubes (especially important in the case of OEM customers that might send back entire batches of tubes), but avoid possible consumer complaints about "stale" tubes. Other systems prefix the number with the letters JHS or JAN. Confusingly, the British also had two entirely different VT nomenclatures, one used by the Royal Air Force and the other used by the General Post Office, responsible for post and telecommunications at the time, where it may have stood for Valve, Telephone; none of these schemes corresponded in any way with each other. One system prefixes a three-digit number with the letters "VT", presumably meaning "Vacuum Tube". Like the British military system, these have many direct equivalents in the civilian types.They generally follow the following format: (example) 322 5904 where 322 is the manufacturer code (in this case Tungsol), 59 is the year (1959), and 04 is the week.One alternate scheme is: 274 940 274 is the EIA code (RCA) 9 is the last digit of the year (in this case 1949).