Originally Posted by Timbre Wolf
Here's a factoid to further confuse tube i.d. issues: "Siemens"-labeled tubes have often turned out to be RFT-made (East German company, not the West German Siemens). The "=" with a slash through it is the etch code symbol for true Siemens tubes, such as those you've got labeled "Valvo."
Thank you. Yes, I am aware of the RFT/Siemens thing and the significance of the "=" with slash. Apparently, some tubes -- EL34, I think, labeled Philips were also made by RFT, while some Philips-labeled EL34 tubes -- Philips owned Mullard -- were made in the Mullard Blackburn plant. And, I have some RFT-made EL34 tubes for which I paid $70 for the pair -- a veritable bargain in NOS EL34 tube land -- that are incredibly good. And, as is readily apparent from this thread, I am a piker and newcomer to this.
Thank you again for all of your help. I really appreciate it.