Unless you run the tube in your amp or a similar amp and knows what to measure, there is no guarantee that you are buying a "Match" tubes. Most of the "Match" tube advertised have close or equivalent Gm (transconductance) measurements when measured with a tester. While when you run a tube in an amp, this is not the only parameters that are important.
My experience: Like you, I still have a Dynaco ST70. In my quest to get a match set of Mullard tubes, I had tested at least 10 to 14 pieces before I got lucky with a quad and returned the rest. Some have high Gm measurements, but does not bias in the amp. You see what I am getting at?
Test it in your amp and see if it holds bias, then compare the GM on a tube tester. Buy from a seller that have return policy or accepts replacement.
My experience: Like you, I still have a Dynaco ST70. In my quest to get a match set of Mullard tubes, I had tested at least 10 to 14 pieces before I got lucky with a quad and returned the rest. Some have high Gm measurements, but does not bias in the amp. You see what I am getting at?
Test it in your amp and see if it holds bias, then compare the GM on a tube tester. Buy from a seller that have return policy or accepts replacement.