My interpretation of Styles' line is that back in the 22nd century the presence of the birdy paint job was the ONLY constant between numerous ship designs of the Romulans. That's quite apart from the fact that a century had passed between the two superpowers without any (known) contact
That seems the most logical.
There is a limit to how much (somewhat) real world logic one can apply to this, but the question arises: just how far is Romulan space from Earth? Was Earth ever really in jeopardy during the war or was this war mostly on the frontier (as far as Earth is concerned)?
The Romulans are offshoots of the Vulcans. Were they transplanted, maybe by the Preservers, or did they migrate off Vulcan on their own? Post TOS books and later productions favour the latter, but when BOT was being made that was not established. Spock certainly didn’t elaborate on this point.
If we accept that Vulcan is not that far from Earth (accepting 40 Eridani as Vulcan’s home star) then in extent Romulan space mightn’t be too much farther from Earth either. If Romulans left Vulcan at some point in the past (in “primitive” ships) just how long could they have been in flight and how far did they get into space (and in which direction)? One of the older Pocket Books dealt with this subject decently and suggests Romulans were in flight for a few centuries and thus managed to get some distance from Vulcan. If this all happened within, say, the past thousand years then neither Vulcan nor Romulan really developed much in terms of spaceflight—they had interstellar spaceflight centuries before Earth and yet they were no more advanced than Earth when they came into conflict in the mid 22nd century or when they crossed the Neutral Zone in TOS.
So this gets us to the next question: considering distance and level of technology: what was more likely—a war of about 4 years duration as put forth in the Official Chronology or a conflict of 20-25 years as put forth in the James Blish adaptation of the original episode?
A short duration conflict still allows the Federation to be founded in the latter mid 22nd century whereas a protracted conflict pushes the founding into the late 22nd or maybe even early 23rd century. And note that in TOS there seems to ba subtext suggesting the Federation isn’t all that old, maybe only a few decades by the time of TOS.
Yeah, yeah, TNG and the rest “officially” establish the bare bones backstory, but in 1966 none of that existed yet, so it’s still largely a blank canvas.
So what have we got?
- WNMHGB establishes FTL ships exist in the mid to late 21st century. Early ships are essentially cylindrical in configuration with a space warp ring or rings to create a warp field
(as already conjectured upthread).
- Earth/Romulan war set about 100 years before TOS.
(Does this mean it started 100 years prior, ended 100 years prior or the mid point is 100 years prior?)
- “Primitive” ships with atomic weapons.
(I think we can also assume energy weapons also existed.)
- Subspace radio, but no visual communication.
(This doesn’t preclude any in-person face-to-face contact if any presumably destroyed ships were actually taken and the crews executed or taken hostage. Knowing your enemies physiology could be valuable intel. Suffice to say neither side appears willing to own up to this possibility.)
- Jose Tyler’s remark in “The Menagerie” that “the time barrier has been broken” might simply mean TOS era ships are significantly faster than what came before
(possibly due to Daystrom’s more advanced duotronic computer systems that can handle the complex computations of navigation and propulsion systems management at significantly higher warp speeds).