Correct. I called Mesa with mine. They did not have an exact finish date for my serial number, but could provide a ball park based on SN.
They go in sequential order. Here is what he told me when I asked about my Dual Rec. They started making the Dual Recs in 92. They went to the 3 channel design in 2000. At that point they were somewhere in the 15000 range. Mine is in the 17000 range and he said that would put it somewhere around mid to late 2001.
That may not help you too much depending on the SN on your amp and the model.
