This thread has me nostalgia-ing hard.
I remember when I got my Mark-nothing, used, I had some questions. Called Mesa, and Randy, as he was known back then, answered the phone himself, talked to me for a long time, about possible mods I could do myself, integrating an Alembic F2B as an independent clean tone, etc. (Amp was one channel, only switching was a footswitchable boost that basically dimed all the tone controls, so a separate clean path was really useful.)
If I'm not mistaken, Mesa was Randy's garage at that point. My amp had labelmaker labels on the back, serial B-0015.
He really did change the world. Not a lot of people have that kind of impact.