Which brings me back round to that question of why Decker's Constellation was NCC-1017. Could the Constitutions have been around longer than we taught ourselves to believe? Was Decker's ship part of an earlier batch of them?
In that "Class" versus "Mark" model, I think that's very likely. The problem is that there's just no way to know for sure. The primary reason that I started this thread in the first place was the thought that if we can establish that the one registry on the chart is 1864, we can definitively answer one question with no doubt: are all of the registries on the chart Constitutions? It's the only question, given the data we have, that I think we could answer definitively. Everything else is informed conjecture at best.