The Gold 6SN7EH features gold plated pins for superior contact.
From EH: "High quality 6SN7 tubes have virtually disappeared... until now. The 6SN7EH tube is a beautiful sounding tube, on par with RCA's red base 5692 tube. It maintains a linear response while being able to accept a full voltage. Vintage tube amp users and audiophiles will be thrilled to find that a superior quality, ultra low noise replacement 6SN7 tube finally exists." Other Electro-Harmonix tubes6SN7 Tube Types