Tested Matched Pair of National Union 7A8 Tubes with original Boxes.
Date Codes LU.
The date codes on the tubes are the same as the date codes on the front tabs of the boxes so you know that they are the original boxes that they left the factory with.
Tubes are closely matched for mutual conductance testing (GM), date codes and internal structure - of which they are identical.
Tested on a calibrated Hickok TV-10 military tube tester and exhibiting no shorts or leaks with the following results:
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