Welcome aboard John!
Assuming the "backstory" is correct (and I have no reason to suspect otherwise), I'd bet that's a Corona built JF30-12.
Lack of s/n stamp on headstock in particular makes me wonder if it might be a "first article", ie, a piece built 100% to production standards and using production techniques to ensure everything is as it should be before commencing production.
We know when Fender moved Guild to Corona all their builders needed to be trained in acoustic build techniques, and thus there were a lot of "test" and "practice builds" of different models that weren't intended for retail sale, thus no s/n would be needed..
And that might explain how the head of the Corona Custom Shop got hold of it.
But that's sheer conjecture on my part, we just know it's extremely rare to see guitars without s/n's from prior to '05 when they stopped stamping the headstocks.
The tough part is value: absent the s/n, there's no definitive proof this is a "real" JF30-12 or when it was built. That could be very relevant to a "collector" who might believe these will increase in value in future, and it makes an appraiser's task that much more difficult if for example some build periods are more desirable than others.
I'm not aware of that with JF30-12's, and they're not particularly "collectible" except maybe to guys like us, but the principle still applies.
And take into account the corollary, if there's no s/n, how do we know it's a guitar that
was built to production standards and not possibly doomed to a short than normal life because it was simply a test bed for an untried build technique that didn't pan out?
I'd look for an appraiser who's got experience in musical instruments for a "real" appraisal.
Given JF30-12's in very good condition with case are probably $2k-2500.00 in the market right now, it's not like we're talking a potential loss of tens of thousands or anything, but the lack of s/n might put off a serious buyer. Having an appraisal at least may help 'em feel comfortable with it, that it's "for real", for example.
What would be best is if you could get a letter from Mr. English describing guitar's provenance. That might actually
increase value, but without it, you got nothin' but a story, no snark intended.
It
does look like a real nice piece.