Please find for your consideration a NOS ( new old stock)  6SK7 tube.  Tested.  These tubes have been languishing in a collection of tubes for many years.  RCA and GE.

Please examine the pictures carefully.  They constitute a good part of the description.  The picture with my tube tester is a general picture only and does not show this particular tube under test.

The tube is being sold as-is.  However, if it is not as depicted in the pictures, I would consider a refund.