Strange how many used valves measure NOS?

Maybe I have been lucky but many tubes I buy as "used" actually test like new. I have only once gotten a dud - a 6AB4 I bought on ebay. I disregard the NOS label until I test them myself.

I recall reading (I think) that many tubes will test in the new range even though they are used. But at some point test wise they drop off the table (not a smooth curve between new and used). Don't hold me too it though.

Tested more today and the tester died - solid state here we come! Only joking.
Strangely some definitely nos tubes I have test mediocre but sound fine and some that test brilliant are noisy as hell in the amp.
Will have to sort and calibrate the tester as it's strangely addictive - like the lottery I suppose.
I must admit to having had :-(visons of sparks, smoke and spectacular explosions but it was good as gold whilst it worked.
Strangely enough there are still places here in the UK that sell good valves at reasonable prices, just a shame that I prefer US of A valves over the soupy examples of Brimars and Mullards I have tried.
If I ever manage to get my dream amps (lots), I'll be a paranoid wreck given the price of replacement tubes.

Finally someone has had the guts to tell it like it is. Yes, there are a number of greedy tube sellers on this site that are less than scrupulous, yet have "perfect" feedback because foolish audiophiles believe the lies and misrepresentations. These same audiophiles don't know the difference, and are blissfully ignorant that they have purchased used, poorly matched, and mediocre-sounding tubes.
These same sellers go to hamfests and flea markets, picking up old, used tubes, and then pawning them off as NOS or near NOS on the innocent.

Beware of just following feedback on these tube sellers for these very reasons.

Jim McShane and Kevin Deal have very good reputations, as does Andy Bowman @ Vintage Tube Services. Some of the prices are unjustifiable, in my mind, but silly audiophiles have driven this madness this far, simply by being willing to pay these exorbitant prices.

NOS = New. A new tube will look new, 90% of the time. If you know how to look at it, you can tell JUST from that. The lettering, the base, the pins, the flashing.

I also have been told that tubes with many hours on them can measure "NOS", but their life is past the 50% mark. Eventually, a decline in the reading will plummet.

Buyer beware.