Tube Question-Help

I receive a quad of old El34s. They all test fine, however I notieced 2 things which I need to know are potential problems.

1. on the top of one tube where the silver is, the is a hole in that stuff so you can see down into the tube (the hole isnt in the glass, but the silver coating.

2. on that same tube, I noticed on the main part of the tube the metal part (just inside the glass)is faded to where you can see more of the heated elements inside the tube than on the other 3 tubes. If you look at the faded part it looks much like a water spot, it appears that area has thinned out which is why you can see into the inner area.

sorry for the lame decriptions, but it is hard to describe.
De2d307d e5fa 40ba 9fc0 0d95b5a6df5djustlisten
The silver is called the "getter", which I believe is Magnesium. It is fired after the tube is sealed to burn off any Oxygen remaining in the tube envelope. There is a little metal halo in the tube where the magnesium was before it was fired. After the firing, the magnesium leaves this silver area which has no further use and is of no concern. Don
I agree that what you are seeing is the getter, but not that
once it is fired it has no futher use. I am in R&D in vacume tubes ( very high voltage X-Ray tubes ) and the getter keeps working through the tubes life. As you use the tube it will
burn metal and imperfections off the plates and form gasses
that the getter sucks up like a spunge for lack of a better way of simply putting it. As the getter is used up it will fade. Your tube may test good but is on its way out. Rember you can have a tube that test good and does not preform well. If there is any question as to the tube's integrity
go buy what you hear not how the tube test like. For this reason I don't buy used tubes. Hope this helps. RG Knaak