It is a USN-CW-300B with date code 142. This is a very rare version of. This tube and has black plates as well as a single D getter. Was tested on a calibrated TV7/B-U tube tester (5VAC, ER3-2000, bia...
I have decided to sell a very special Western Electric USN-CW-300B tube from my collection. This tube is incredible both physically and operationally. There are no stains on glass, smudges in the text...