For Tube Folks...

Never had a single failure with Svetlana, SED, SED Black Sabre  EL34 in decades running in CJ, Cary, Latino Dynaco, Prima Luna amps, tese all 90's production tubes. Always heard quality went down in later years.

Ran some GE 6550's in Cary amp, did not like those, all muscle no finesse, EL 34 has always been my fav for push pull amps.

Since we are talking tubes, does anyone know how long 12AU7 RCA blackplates from 50s usually last ? I don’t mean military/industrial Command blackplates. What about 12AX7 Mullard longplates? I understand it may depend on particular amp.

That’s what I use, close to 2000 hours on them.

As a side note, watch out for eBay sellers who offer "NIB" (new-in-box) or "NOS" tubes in "original" boxes.  Some of theose boxes are reprinted stock white tube boxes.  You can usually tell when you see white edges outside the original labelling.  Another tell is identical coding on the inside flaps of the box, indicating there were printed from an image of a single box.

Hi All -

I really appreciate the information. 

A special thanks to @ Viridian for mention the "The straight glass, three getter tube has a side getter so will have silvering on the side in addition to on the top"

I do not want to delve into the what constitutes 'NEW' or 'USED' conversation at this time, but that may be a worthwhile string someday...

My question -  Within reasonable certainty, is this tube is NOS or is it USED?  

@inagroove Just look at the pins of the tubes. If you see scrapes along them the tube has been inserted into sockets a few times. An NOS tube will have no scrapes.