Early 24th Century Ships (2305-2330)
Virtually nothing is known about this "lost era" (which I separated from the mid-24th century just because I sketched up so many vessels from these eras), except that the Ambassador class is developed in this time. The design comes in a number of slight variations and may have been built for a time of two or more decades. The ship is much more voluminous than the Excelsior, and it can be supposed that it is the largest ship type of the time. A further comparison of design features shows that the long angular nacelles of the Excelsior make way for a shorter and more rounded type on the Ambassador. Also, a Bussard collector is sticking out from the nacelle tip again like in the TOS era. Lifeboats hatches are visible for the first time. The Ambassador has many more windows than previous designs, and there are also windows on the top of the saucer. The small phaser domes have been extended to phaser strips which are located on the top and bottom of the saucer as well as in other tactically vital places throughout the hull.
There are other canon ships and ship classes from the era whose designs were never shown. Furthermore, the Centaur and Curry may have been developed in this time, although their Excelsior-derived components are older and therefore not necessarily typical of the early 24th century.
The maximum speed of the ships of the era is mere speculation, but it is probably around Warp 9 (new scale). Registries are from below NCC-10000 to about NCC-40000.