I have some of the Pinnacle USSR tube marked as 6J5GT for convenience all about as matched. I bought 6 as it is never a good idea to buy just the number you need in case one goes bad or they don't really match. Four match really well, one is a little high on the current draw and one is much higher. So 4 out of the 6 are truly matched. I have no idea of the dates for these tubes as the tubes, as mentioned, have been scrubbed.
I also bought some from Ukraine that are rebranded and I marked them as 6J5 as convenience as that is also how I measure them. Out of 12, most of them match pretty well, with a couple of outliers but not bad. They range from 1961 to 1969 (1) as the tubes are not scrubbed to get rid of the factory printing, which is always a shame to do. The tubes all have testing on them but they don't match what I get for measurements and don't test as close as the measurements indicate on the tube, which is why I always want to test my own tubes.
These tubes need at least 50 hours of play time. They start out pretty nice and then for me, go a little flat sounding, lacking in dynamics and transparency and then come back and pass how they originally sounded but they need plenty of hours on them.
For some cases, matching isn't real critical but in the input stage, you can get an imbalance if they aren't close. A follower tube will have little effect on this, depending upon how it is being used.
I still need to measure or flip the MKII over and look at the circuit to see if the 6SN7s are in parallel (reduces noise but also increase gain) or how they are connected. Andy could let everyone know.
I had one 6S5S, or what ever they are called, with the shielded plate (USSR), die. The heater did not light up. Ok, about 50% of the time the heater doesn't burn out (filament) but the connection as they are old, can be bad. So I resoldered pin 2 and 7 and it works now. So don't just toss a tube if the heater doesn't light up. It could just need to be resoled as this solder is very old. And, in this case, contrary to what I normally do, I only bought 4 tubes. :^)