The Devil said:

Mine have copper foils. They're better than yours.

Oh yes, when they turn green, they sound best, don't they? LOL! ;-)
]
PS. I have some "diamond-bottomed Siemens Valves" for sale as well.
Tested on a snake oil tester, they were all 110 % !

I fixed that diamond-bottomed Siemens problem with my gas stove and
branding irons (which I keep for my slaves).

Are you feeding them well enough?

--
Sander deWaal
"SOA of a KT88? Sufficient."