TOS Era Ships (2200-2260)
The Constitution class seems to be Starfleet's most important ship class during the famous Enterprise five-year mission in the 2260s and was the only known canon class of the time (although TAS would add a few more and we have the TAS-based USS Antares since the remastering of TOS: "Charlie X").
The class history of the Constitution dates back to the more or less conjectural year 2245 when the USS Enterprise NCC-1701 was commissioned, as the second ship of her class as it seems. The main hull of the Constitution class is a flat round saucer, the engineering hull is cylindrical. The overall color is light gray, the hull panels show only a slight contrast, and a shield grid is faintly visible. The warp engines are simple tubes with red glowing Bussard collectors at their forward ends. If there is a warp field grille like on later ships (and on NX-01 too), it is on the inward sides of the nacelles. The original Constitution class has a metallic deflector dish sticking out from the engineering hull. Standard armament consists of phasers and photon torpedoes, but neither weapon array is clearly visible on the hull; both seem to be located in the saucer's lower sensor dome. Although the ships must have something like thrusters, they cannot be identified either.
Registries are below NCC-2000. The cruise speed of teh Constitution is Warp 6, the maximum speed around Warp 8 (old scale). We can assume that most if not all other ships of the era are considerably slower.