The DC's are great amps. I have 2, a DC-3 & a DC-10.
The DC-10 is 6L6 only. There is a mod to be able to use EL-34's, but it is intensive. It requires removing the filament wires from the main board to the power tubes and then installing a second filament transformer just for the power tubes.
Don't try this at home.
As for production, my DC-10 is serial # 99, I did not look inside the chassis for a date code though.
I have had DC's from '93 I think, it gets hard to remember after a while. Too many amps since then.
You really can't go wrong with them if your budget is tight. Mesa makes amps that do things better, for instance....
Lonestar = much better cleans and reverb
Mark IV or Rectifiers = much thicker distortion types
BUT....The DC's are the best all around amps that are the easiest to dial in out of most of the Mesa line. I also have a Blue Angel, which is incredibly easy to dial in, but it only has 5 knobs on it and only 1 channel.
The DC's are also some of the easiest amps that Mesa made to modify. I have done many things with them with great success.
Hope this helps.