[Arran]

And further to my last past I was told that these are the ones not to buy. They don't sound as nice and don't last as long. Maybe Morzh can enlighten me as to what the difference would be between them.

http://www.ebay.com/itm/PLATINUM-Matched...SwGzlTu6zY

 The listing says that they are made by Reflector, which is the same company that makes Sovtek branded tubes, just older stock is all. I don't know why they say that there is anything wrong with them as opposed to the Sovtek ones. I believe that the mill spec tested ones have a pentagon shaped logo on the glass that says "CCCP" inside, as Mike says that just means that the tube got a passing grade for military use. So lets say they needed 500 5U4s, so they tested as many tubes as they needed off the line until to meet the quota, but that doesn't mean that the other 1000 5U4s they made that day were junk. I'm just taking a guess about how they did things since this was pretty much how the U.S or Canadian military did things, like with JAN numbered tubes for example where they say VTXXX.
Regards
Arran
Regards
Arran