(1) Tested Raytheon 6BK7B Tube with Original Box.
Date Code F12. Made in Japan.
The box shows staining on one side panel as well as the front tab/flap - see last two photos.
This tube tests above NOS.
Tested on a calibrated Hickok TV-10 military tube tester with no shorts and no leaks with the following results:
Gm Test = 8750-8625 micromhos
Minimum pass/good = 5350-5350
Average NOS rating = 8025-8025
