The 6H5 was registered by Raytheon in 1936. Every example seen was either branded Raytheon or Silvertone. The 6H5, as registered, has the characteristics of a 6G5 but also has a stationary shadow at the top as well as the normal moving shadow 180 degrees opposite at the bottom. One also sees examples dual-marked “6H5/6G5” and these are simply 6G5 tubes and do not have the extra shadow. (Information from Jim Cross)
