2 x NOS STC Standard S4020A AR12 R87 102D Triode Tube, V.GOOD, Tested, Vintage A

S4020A – 102D – 4020A – AR12 – R87 – 3A/108A – 4631 – CV1664 – SY4020A. Standard / S4020A. These Standard tubes were manufactured in England during the 1920s and 1930s. They are a very hard-to-find triode from the golden age of vacuum tubes, and the sound quality is reported to be very, very good.

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