[Hallicrafters] to get the best (warm) sound from the 6C4's

[Jammer]

 "..in order to get the best (warm) sound from the 6C4's, even if they are used in 
 an RF circuit,  you MUST paint the very tip of the glass with a green felt tip marker."
   - 73, Charlie k3ICH

   O-kay... but which of the approximately 67 shades of green works best?
   It's not listed but I'd bet a good one (at least for the guy selling the tube)
   would be dollar-bill green.
   
   73, Terry KC9KEL