The concept behind this is to imagine the predecessor to the Constitution Class and what a refit of that might look like. A bit of an odd concept, I know, but it was mostly an excuse to model an idealized Phase 2 Enterprise without having to be tied to established details. I also really like the first and second pilot Enterprises and wanted to retain some of the details and proportions of those, such as the taller bridge, larger deflector etc.
So I imagine the Declaration class was launched in the 2230's but relatively few were built because the upcoming Constitution class design was so much better. The ships were refitted in the late 2260's but by the late 2280's they had all been retired. The refitted Declaration class is 257m long as opposed to the Refit Constitution at 305m so it is substantially smaller.
I might eventually also model the ship as it appeared in its original 2230's configuration.