has anyone else experience this.....

I agree with Al, that NOS should mean the tube has not been used in anyway whatsoever, however this is usually not true in so many cases.

Here are a couple of good articles by Brent Jessee about NOS tubes,

NOS Tubes: New Old Stock or Nasty Old Stuff?

A BRIEF NOTE ABOUT NEW OLD STOCK TUBES

Brent Jesse is a very reliable seller, but IMHO, some of the NOS tubes may possibly be slightly used, however do exceed rigorous testing for NOS. I have read many times that even a good slightly used old tube can still be much better than some of the new production junk. The problem lies with everyone acquiring old tubes calling them NOS regardless of the condition..

I used to questioned NOS tubes that did not come in original box, however found out that this means nothing. A poor used tube can easily be place in an original box. The box of a NOS tube may have deteriorated over years. Also, I have some very rare NOS Brimar black plate 12AT7's from 1955 that came in a bulk pack of 100, so no individual box, however, I do have the original bulk box.

Elizabeth also brings up a good point about tubes being relabeled, so it is important to know the physical characteristics of the internal structure for a particular tube.

It is always best to purchase from a reliable seller that offers a guarantee.

Al, you're welcome. Always glad to provide helpful information.

The Brent Jesse site also has a lot of other good info about vintage tubes, as well as some instructional videos identifying certain vintage tubes. The following websites have many pictures of vintage tubes that may also help with that vintage tube identification.

tubeworld

tubemongerlib

I acquired the Brimar 12AT7's many years ago that I previously mentioned, and for quite some time was unsure about them being authentic, as they were different from all other pictures of Brimars I found. After finding a picture on the Tube World site, I then felt they were a real vintage tube. This was also confirmed when I allowed a few local friends to try them, and they did not want to return, but asked to purchase them.

BTW, I also have tube testers, a B&K 600 for quick simple testing, and a Hickok 752 for more serious testing. Although the Hickok seems to work reasonably well, I am curious about your thoughts on calibration of this tester.

Tony

Al, thanks for your comments, as that makes me feel better about my 752. I have had it for quite a few years, and over that time the results have always seemed to be consistent.

Also, some of my tubes came from my dad's shop, as he was a radio/TV serviceman, with many others coming from different shops in my area. I also collect some antique radios, mostly Zenith, and some HH Scott tube gear.

Cheers,
Tony