[Amps] OT: Can someone ID this tube and its use ?

[Gary Smith]

> > How about a picture of the bottom of the tube - it looks like either a
> > 3-400, a 4-400, or a 3-500.
> >
> > Try fogging the side of the envelope with your breath - sometimes that'll
> > bring out a faded number.
> >
> > 73, Pete N4ZR

I believe one of the tubes that is reminding me of ended with a "C" 
like 4-1000C for example. One of their old catalogs from the 80's 
like I have in Indiana would have some decent photos to refer to.

Along with Pete's idea of fogging it, sticking it in the deep freeze 
before doing that to reveal faded numbers will also help to bring out 
the contrast in the "fog"

73,
Gary
KA1J