[Amps] Help identifying tubes

[Ken Brown]

They are definitely not 3-500 or 3-400, because those don't have the 
metal bases. 4-250 don't have fins on the anodes, so would have to be 
4-400, unless it is a pentode. You could probably figure that out with 
an ohm meter and the data from Eimac (or descendant) site.
> 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.
>
>