So there's reference out there that any tube with the stop sign logo with 6SN7GT in it, Sylvania tubes for example, are most likely made by RCA. 0.o What the Mercedes!? #blasphemy
https://www.tubemuseum.org/SearchRe...is is why we see,at some time relabeled tubes!
MEANINGLESS CODES by TUBE REMARKETERS:
"Both Tung-Sol and RCA utilized the "Stop-Sign" logo [5751] in brackets. The "hole" in the top mica identifies these USA made tubes from the TUNG-SOL factory in Newark, New Jersey, USA in the 1950's.
THE UNITED-ELECTRIC RELABEL CODE 88-37 IS MEANINGLESS AS THEY SIMPLY RELABELED NEW OLD STOCK TUBES FROM TUNG-SOL. RCA, SYLVANIA, AND OTHERS. NO ONE MADE D-GETTER OR SQUARE-GETTER TUBES IN 1988! AND UNITED-ELECTRONICS WAS OUT OF BUSINESS IN 1988! SO 88-37 WAS UNITED-ELECTRONICS INTERNAL NUMBERING SYSTEM AND DID NOT SIGNIFY ANY MANUFACTURING DATE.
Especially, during the 1950's war effort, it was a common practice for USA factories to source tubes from each other and re-label them. 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 ... 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.
UNITED (United Electrics Company, Newark, N.J., USA) was a company that simply re-labeled Tung-Sol, RCA, Sylvania, and GE USA made tubes for resale".