Of the known canonical classes, there does appear to be a pattern. The class leader has a lower registry than its sister ships.
probably had a registry lower than 956, and the class was probably in service on and off for over a century, maybe longer. The latest Haynes Manual, on the Rotarran
, does suggest a possibility. Like the Klingons, Starfleet constantly updated the internal hardware and software of their ships. The exterior was largely kept the same, save when there was technological advances to be gained from changing the exterior.