True NOS has little to do with test results. True NOS is a tube which has never been in a circuit other than a tester, which can be hard to discern at times. Most true NOS come with original boxes. Being NOS doesnt make the tube better it just means that the tube has never been used. Tests NOS is not true NOS. "NOS in white boxes" is rare and it is a misleading and some would say dishonest claim.
Further, I have seen up to a 20 to 25% variation in the test levels of true NOS tubes from the same family and manufacturer. Add to this the fact that each tester is idiosyncratic by tube type and you quickly understand that the average NOS reading listed of a particular tube is kind of a fiction.
Further, I have seen up to a 20 to 25% variation in the test levels of true NOS tubes from the same family and manufacturer. Add to this the fact that each tester is idiosyncratic by tube type and you quickly understand that the average NOS reading listed of a particular tube is kind of a fiction.