Cunningham 71A tube, in Tektron preamp (Italian company), this tube in production from 1927 to early 40's, don't know exact date of mine. Also have any number of various 50's era tubes running in a number of components.
oldest tube(s) in your system
Please let us know what they are running in too. Thank you for your attention to this matter...ha!
2 x 1949 Sylvania ladder plate 6BL7GT (in monoblock amps, custom built 2 x 6BL7GT + 4 x KT77)