I have a quad 6N15N-EB  I picked up some years back..  NOS as far as I can tell.. All labeling intact.  
Dont recall if they are a matched quad.   Tested on my tester and test good.
$70 for the quad---Can be seen on US Audio Mart

Also,  have a quad of purportedly Siemens el84 with most all labeling wiped off with bits  of "Germany"  seen on a couple. --will post soon on US Audio Mart.  These were acknowledged by a tube monger that they are Siemens FWTIW.  

All of these show no  discernible signs of being used.  

  pair  of  EI  el84 left with  all labeling intact.   can be seen on US Audio Mart

I also have more than a few of low hours SV83's with the proper logo.  --I just looked at these and some appear unused.   label fresh and not heat affected.  

Found a  matched  SV83 Svetlana quad bought from Antique Electronic supply at least 10 yrs ago or so.   In boxes with part of the sticker enclosing the quad indicating matched quad.    --$70