X200A

Common type USA tube/semicond. Ace Electrical Laboratory; Newark, NJ Champion Radio Works; Danvers, Massachusetts Croydon (where?) Duovac Radio Tube Corp.; Brooklyn, NY Hygrade Lamp Co. (Neptron); Salem, Massachusetts Hylon (tubes), brand Knight (tubes), brand Mellotron Tube Co.; Chicago, IL Neptron Corporation; Salem MA (subs. of Hygrade Lamp Co.) OK (tubes), S.S. Kresge Co.; Detroit, MI Sky Sweeper, Charles R. Ablett Co.; New York, NY Sonatron Tube Company; Chicago and New York Star-Ko (Starko), USA