[Amps] Help identifying tubes

[mike stokes]

Hi Guys

Someone gave me 2 tubes years ago and said they were 3-500s.  Well I am not
sure they really knew, and I don't know as the lettering is worn off.  Here
is a link with some pics.

http://picasaweb.google.com/mike9v/Tubes#

The one on the left is an Eimac.  It end in an A and has S4    7704 stamped
inside.

The one on the right is a Westinghouse and looks like it says 5/5xxA where
the x in worn and illegible.

Any ideas on what these really are ?  Or what is a good way to figure it out
?

Any help is appreciated.

-- 
Mike Stokes
KK9V