The annoying thing there is that
Sabers are among the least numerous ships witnessed in DS9. Apparently, either small size doesn't equal mass production after all, or then the small ships produced in great numbers get vectored to completely different theaters of operation (perhaps because they are too small to take much part in the fights where the bigger ships are numerous).
In the span of only a few years between the TOS and TMP eras, we had four design types (TOS Constitution, TMP Constitution, Excelsior, and Oberth) that were contemporaneous with each other but looked nothing alike.
And one was supposed to represent a "looks" that was bowing out even when we first met her, while another represented the future that was about to begin, leaving one "middle note", and then the
Oberth...
It's possible that one era has many different looks, especially by virtue of having overlapping old and new looks. But is it possible for one look to be spread across multiple eras? Not just in the sense of ancient ships soldiering on, but in the sense of new designs on that same vein being introduced? The persistence of
Mirandas to the 31000 registry range isn't quite the same thing; only the introduction of an all-new design with LN-64 and the thin saucer but a registry in that high range would.
Timo Saloniemi