Tube vendors.

Andy, Kevin Deal and Brent Jesse all know what they are doing. Certainly one of the best is the guy in Wisconsin (Brendan?) and Gregg Levy at High Test in New Jersey for guitar amp (pro) tubes. 

I wouldnt buy from any dealer that says they have a bunch of: "NOS in white box" tubes. Should read "tests as NOS in white boxes".

I won't try to tell you what to buy, audition_audio, but tubes were bulk packed for industrial and military users.  So NOS tubes can come in white boxes.

Krelldreams...from the original Russian tubes I ventured into Sylvania "chrome domes," new Tung Sols, and others I can't remember but stuck with a quartet of NOS GE 6SN7GTBs which have lasted a very long time.

Yes there were, but when you see large quantities of NOS in white boxes that arent JAN or industrial and there is only 1 seller making this claim it should give you pause. True NOS is like being pregnant....you is or you aint. Original boxes dont prove NOS, but they are a very good indication. 

All the above are excellent sources for tubes
Richard Gray , my tech geek swears by Amplified Parts, so thats where i now get my 12 power tubes, 4 sets of trios, Not so easy to match, which AP does their best to fulfill,. RG says they have excellent  testing equipment to match. 
My next set will be EH KT88's.