For Tube Folks...

The pic you show has a very large side-getter patch (good), with light-gray fringes that indicate some light use - roughly consistent with the seller’s description. As use continues, the side patch typically shrinks (well before the top patches), with the fringing sometimes becoming more dominant. I have some GE 7581A with chrome side patches and NO fringing, that are probaly truly NOS. Anyways, to see a very large side getter patch on a power tube (dark metallic or chrome, NOT chalky white/gray or brown) is usually a good sign. (note: if you see a side patch on a tube that shouldn’t have a side getter, like an EL34, that’s bad news lol)

The debate on "NOS" nomenclature is boring semantics. NO I wouldn’t call this tube strictly NOS, but these days very few tubes left are. If the seller’s description is accurate, and seller can be trusted, I’d be happy with ’em.

+1 atmasphere

I examined the pins when I cleaned them.  All showed light-ware - a sheen that indicated they were inserted into a socket.  I was not alarmed because the seller's description indicated that they had been tested and had some burn-in hours.  Perhaps I should have thought twice...  

"An excellent lot, matched to within 5 percent and then aged in a hi-fi shop demo unit. Very low hours, burn-in time only, and the performance has been verified by us..."

Regards,

+1 mulveling

Thanks for the details regarding the side-getter patch-chronology - very helpful.

As a novice, this is my first tube with a side-getter as well as my first 'NOS' tube purchase.  If I purchase another, I will be better informed...

Regards,

NOS   New Old Stock, usually from old inventory from out of business retailers. Boxes can show significant shelf wear.

Even new tubes are tested by resellers before they're sold. A while back, I bought four Telefunken military grade tubes for a radio multiplex. I got them on eBay and the seller was, I believe, an old Ham Radio Operator and these were from his own collection. He had an Amplitrex tester and was very transparent about the whole process. I just had to make the decision on whether or not to trust him and now, I'm really glad I did. But this was long ago, way before the insane prices that we now see for NOS Telefunkens. 

Currently I'm in the market for a Linlai E 6sn7. I've decided that there are some new tube manufacturers that offer a better value than those highly coveted Western Electric, etc... Plus when you by a new tube, it comes with a warranty.