Misschien kan dat toch wel...
Philips buizen komen ook niet allemaal uit Eindhoven

Ik vond dit stukje:

From what I understand, National Electronics was a tube manufacturer (early-on) and later a rebrander/distributor located in Illinois. I originally thought they only added their label to tubes made by other American manufacturers but I've seen sites showing tubes like nixies, etc., that stated the manufacturer was National. Richardson Electronics snapped the company up years ago and still owns the name. The National re-labeled tubes could be a few different brands. It is highly likely that they are American made but not made by National.