Thanks for revealing their negligence. I hope that it costs them future business. At very least, they may see this post and be shamed into making you whole.
The REAL St. Petersburg, Russia Svetlana plant met its end in 2012.
Their 300B's were the best sounding and most unreliable 300B's that I ever used in an early production Audion Silver Night stereo DH/SET amplifier.
I much preferred them to WE's (screened logo on base) and everything else I tried @ the time, which was early on this century.
Out of 4 pairs only one pair made it past 500 hours without failing (sold that pair with the amp).
A few other users with super slow start up power supplies (Border Patrol comes to mind) had much better results, but also failures as well.
Not a vintage tube that I would seek out unless you have super slow start up and only listen a few hours a day.
I have had the same problem with vintage (engraved base) Visseaux 2A3's in that out of 3 matched pairs I am now down to one pair.
I'm saving the last pair for (at a minimum) a 5ar4 rectified 2A3 amplifier.
I recall other online forum complaints about JAC or JAX, but not the details.
Thanks for your comments, guys (and gals?). I can't say anything bad about their tubes. I think they are first class, sound great and I accept you get a dud every now and then. It's the way this was handled - or actually not handled. Great tubes - not so great distributor. I hope this will spare others from a similar experience.