Hey, thanks for the link, I'm high bidder now.
Don't worry, I'm not bidding very high, I'm supposedly stopping tube acquisition operations. I believe that most of the metal base-type tubes are either made by Philips or Telefunken. The TF are even rarer, I don't have any.
I think that these metal base are better than the Mullard xf2 with the O2mk1 and O2mk2, though the difference isn't very large. The xf2 will do nicely, definitely. But the metal base have that extra refinement, clarity, etc. They do everything very well, bass quality, bass quantity, treble extension, treble clarity, midrange body and smoothness, blah blah blah.
There are no weaknesses. Just think of perfect, and that's the O2mk1 + BHSE with Philips EL34 metal base!