@@ceylonmooney generally yes ,you are abslutely correct, but in the case of RFT they used to produce under a mandatory year plan "Jahresplan" in german, as many socialist countrys did. A former worker told me they produced ECC83 which are the same plate design and wiring, those with marginally lesser gain were often labeled ECC81. They could assure the quality of ECC83 especially for export, but still had outstanding ECC81 aka original ECC83. Try it out, you will not regret it, there is no risk for equipment with this.

That's a possibility, but you're the first to express any interest, so probably not. In order to justify the high cost of introducing a new kit we would need to know we could eventually sell at least 50 units.

​@@tubelab194is it for varios tubes, as there are 2 spots of tubes empty, and the others were lit up?

Most of them even flash.

No it's a Matsushita, made in Japan on Philips/Mullard equipment to what very much looks to be the mullard construction. But they're not exactly the same, that's because the materials used where probably mostly sourced in Asia and of course Matsushita had it's own plant and workers. How did this happen? Philips was big on collaboration with other manufacturers who had significant market share in regions they didn't, so they made trade deals that gave them market access and at some point in the future they hoped to be able to buy the company whole if trade laws allowed. This happened all over the World as Philips consolidated their market share. The first major acquisition that Philips made was Mullard in the late 1930's.

The Telefunken smooth plates are great sounding tubes, but they were never made in large numbers and are basically unobtanium. What we focus on are vintage tubes that are actually available, in enough numbers for good testing close matched pairs.