Chinese built 12AU7 tube. The now closed Beijing Tube Factory made this 12AU7 tube. The factory closed in 2005 and these would now be considered Chinese NOS (New Old Stock). Some folks like this tube better than the current production tubes out of the other Chinese factories.
The 12AU7 tube type is equivalent to the European ECC82 tube and can be used in any 12AU7 or ECC82 circuit.