Interestingly, novelist Voyda McIntyre calls Kirk's ship a "constellation-class" vessel, with lowercase c...
Regarding Matt Decker's ship, there are many real-world examples of ship classes that externally appear virtually identical to some other class, yet have a completely different construction history. For example, prior to WWII, several naval powers upgraded their WWI-era battleships to more modern standards; say, the old Italian Comte di Cavour class ended up looking very much like the spanking new Littorio class, and it would take some careful squinting to notice the lower calibre and different layout of the guns of the older class - and one still wouldn't notice that the older ships were markedly slower and had rather different internal armor.
It would be easy to think that Decker's ship was several decades older than Kirk's, yet refitted to "2240s standards" when Kirk's ship class was introduced, or to "2260s standards" when Kirk assumed command of the Enterprise. Obvious elements in such an upgrade would be the warp engines, the most conspicuous part of the ship's silhouette. Those, and weapons, which are housed within the primary hull - thus perhaps necessitating the reworking of the primary hull to identical shape, too.
As pointed out above, Decker's NCC-1017 is basically the only "out of the line" registry we really have to deal with, as the other oddball regos were for offscreen ships. Until TOS-R used them on screen, that is...
Timo Saloniemi
Regarding Matt Decker's ship, there are many real-world examples of ship classes that externally appear virtually identical to some other class, yet have a completely different construction history. For example, prior to WWII, several naval powers upgraded their WWI-era battleships to more modern standards; say, the old Italian Comte di Cavour class ended up looking very much like the spanking new Littorio class, and it would take some careful squinting to notice the lower calibre and different layout of the guns of the older class - and one still wouldn't notice that the older ships were markedly slower and had rather different internal armor.
It would be easy to think that Decker's ship was several decades older than Kirk's, yet refitted to "2240s standards" when Kirk's ship class was introduced, or to "2260s standards" when Kirk assumed command of the Enterprise. Obvious elements in such an upgrade would be the warp engines, the most conspicuous part of the ship's silhouette. Those, and weapons, which are housed within the primary hull - thus perhaps necessitating the reworking of the primary hull to identical shape, too.
As pointed out above, Decker's NCC-1017 is basically the only "out of the line" registry we really have to deal with, as the other oddball regos were for offscreen ships. Until TOS-R used them on screen, that is...
Timo Saloniemi