U¿ytkownik Finn S. Mikkelsen napisa³:

It's an American Model RCA 813A PA Tube.... Do you have the specs or
du you
have a URL from wich i could find that info, i would be very
gratefull....
813 = Russian GU13, look the
http://www.russiantubes.com/prop.php?t=8&p=175
Good luck,
George SP2BRZ.