What makes Telefunken tubes sound better?


I've reached the point in sampling 12AU7 tubes below $100 per tube where I'm having to buy tube crates to keep the pairs I've sampled. I've tried NOS and new, but out of all I end up back with Telefunkens as having the least distortion and fastest transient response. Yet the Telefunken internals are not the best materials/quality; NOS Mullard CV4003 or the new Gold Lions have higher build quality for materials and precision.

Are there links somewhere that talk to what is different for the internal design/construction of a Telefunken tube? I'd like to support newer tube manufacturers based on educated consumerism, and hope that we can get someone to replace Telefunken at an affordable cost before NOS stock is no longer an option.
128x128davide256
"Unfortunately there are also a lot a fakes in the
market." To date; no one has counterfeited the diamond,
molded into the bottom glass of the authentic(nine pin
miniature) Teles. Easy to spot a phony, or tubes that may
have been rebranded. In the case of Tele's octals(ie: EL34);
it takes a knowledge of their distinct cathode/mechanical
structure to avoid getting burned. A bit of hilarious
Telefunken history: (https://www.youtube.com/watch?v=Lqvvu9ZZfmY)
BTW: Don't give me any static about the stereotyped tubes, in
that video! =8^)
I was told materials used in making NOS tubes are no longer available or banned so quality suffers.

Telefunken 12ax7 and 12au7 ribbed plates are my favorite. Telefunken e88cc is very good but I prefer 60's Siemen e88cc. In my components, Siemen e88cc even best 60's Siemen grey plate Cca.
What I do see with Telefunken 12AU7's that is different from all but triple mica tubes is a mica ramp situated between the plate spacer posts and the getter.