The lower two are fake ECC83 tube that friend of mine showed me....
There is no <> mark on the bottom of the tube.
The logo is silkscreen printed with permanent pigment, the genuine one was made with powder printing which can be easily removed by rubbing on it. So the real one has a inomplete printing of ECC83 logo whereas the fake one has a more complete and beautiful Logo!
I head that some of the fake one even can make a <> mark at the bottom. So you have to be exercise with care when you buy the vacuum tube. The best is asking some expert to check the construction of the plate and getter inside...or buying from a reliable source.
Feverip