[Amps] Capacitor identification

[Pete Raymond]

I am wondering if anyone can identify the manufacturer of this capacitor. 
The markings on the edge
are  "HI-Q HPA 42 BC, 6800mmf +40 -20%.  If I can find out who made this 
capacitor then I can ask them about the voltage that it is rated for.  I was 
told it came off an amplifier and I would like to use it as a plate coupling 
capacitor in a linear but need the voltage rating.

The physical size is 1 3/4" in dia and 1/2" thick with threaded hole on 
either face.

73 Pete N4KW