There were some modern ones from Russia, or Tesla branded tubes that could handle a little more voltage. In general, I think if they are an EL34, they should be OK for anything calling for them. If your wanting to see who made them, a good tube dealer may be able to help you identify them. Good pictures can help too. The 6L6, and some other number tubes needed the letters also. Could be a Mullard, Amperex, or another European, UK, and even US tubes, if they are old stock. I was under the impression you didn't have any numbers, and just ran across them somewhere. Some TV tubes look like they were make on the same equipment, with the same parts, but were totally different inside. This should not be that kind of case, with EL34 tubes.