I have checked all of my RCA handbooks, and they
only list the 6SN7GT.

If there were true metal 6SN7's, RCA didn't want to
talk about them. They must have been made by someone else.

Red RCA tubes were from RCA's industrial tube line. They
were supposedly higher quality than the usual faire.

-Chuck

COLIN LAMB wrote:
I had a few hundred 6SN7 tube pulls. A few years ago, I went through the
entire box looking for a metal 6SN7, for the visual effect in a homebrew
regen. I could not find any. I thought I recalled seeing one, too.

Sadly, this may be the first positive proof that the memories of all the old
timers are collectively failing at the same time.

Not too long ago, I built a regen using a 6SJ7. I knew I had a red RCA
somewhere and looked and looked to no avail. Finally, when I was looking
for something else, I came upon the red one. Sure looks pretty.

73, Colin K7FM