I had a pair of 1964 Mazda 6dj8 that came from Brent Jessee and they were matched section, matched pair. They were some of the best sounding tubes I have ever owned. Unreal tone , unfortunately the preamp they went in is tough on tubes so they didn’t last as long as expected but man did they sound good
About six months ago I bought a 12at7 from Upscale, from Kevin’s Stash It was a Mullard 6201 and it sounds incredible.
The above dealers are a safe bet