I have recently taken the risk to purchase NOS vacuum tubes from a well-known auction site. While they appear original and the sellers have extremely good reputation, I cannot find background information on the origin and quality of these tubes.
In my previous research, the only information that I could find was that a very limited number of other people had the same tubes. I'm guessing they're either copies, rebrands from other manufacturers, or rare. I am looking for vacuum tubes experts who could perhaps help me shed light on these unsolved cases and determine which of these 3 hypotheses is the right one.
Eventually I will give the tubes a listen, which could provide a valuable clue, but right now I am waiting for a fuse to convert the concerned amplifier's voltage to 110V.
Case #1 - Amperex Orange Globes from West Germany
I have owned many Amperex Orange Globes of various types in the past, and it was always of my understanding that they came from a factory in Heerlen, Holland. However, this box of 5 tubes is apparently from West Germany, according to the printing. There is also a code in yellow that I haven't seen before on Holland-made Amperexes. I can't recall if they have creases on the top - I will check when I come back home for the weekend. There are no creases on the top.
Case #2 - Shield-less Mullards
Apart from some military models, all the non-rebranded Mullard 12AU7's that I have seen in the past had a shield logo or a similar shield-like symbol. These, however, simply have the name "Mullard" printed in big characters. They have two faint creases on the top.
Let me know if you'd like any other information, and thank you very much for your help.
Edited by Benjamin6264 - 3/24/13 at 11:58am