The printing on these tubes may be suspect, but the construction is a bigger factor in determining its make. New Sensor (Electro Harmonix and all the Mullard / Gold Lion / etc reissue labels) bought the Svetlana label circa early 2000s, and besides the "S" label they only partially mimicked the construction of the real SED / Winged-C EL34 tube (i.e. the 4 "spring" braces per mica - but even here, note how the SED braces of the top mica go DOWN whereas the New Sensor braces go UP). But they didn’t copy SED’s welded plates, and the top of the tube envelope usually looks sloppier (less symmetric). The linked tubes look more like real SED (St. Petersburg factory, now gone) than New Sensor factory, to me.
There also appear to be some getter differences in the SED production over the years, but the welded plates and top braces should be enough to help distinguish from a New Sensor "S" tube. If I wanted real Winged C I’d take a chance on these, but I’m risky like that lol.
I think I still have 3 of the "real" Winged C tubes in a closet somewhere, from 12 years ago. They were a quad - I can't for the life of me remember how I lost a *single* EL34 from that damn quad. I also had the New Sensor Svetlana at some point. The Winged C are definitely warmer and smoother.
