[Boatanchors] NOS

[telegrapher at att.net]

I'd like for someone to tell me how all the sellers on that auction 
place that can't turn on a radio or remove screws in a cabinet or 
chassis to look inside the radio, "because i don't want to damage it", 
can sell tubes graded NOS.  What makes them NOS versus plain old used? 
How can they tell Which way is which way?  I must be getting to old to 
understand these experts line of thought.

Larry
W0OGH