1958 Mullard 12AX7 ECC83 with the 17mm long plates. I bought this as a true NOS tube and used it for about 25hrs before selling the amp. One of the holy grail 12AX7 tubes. The box and white print graphics are in nice shape. The stamped codes are a little hard to read but I seem to see the desirable “F92” and below that “B8J” which appears to mean made in Blackburn 1958.