Thank you lots and lots to both Krossfader and to Supersonicjazzmaster for providing these measurements, you're awesome.
Now that we have all the needed informations to confirm a theory I had and I've discussed with AcrylicSuperman behind the scenes, I will share it with all of you.
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Given manufacturing tolerance and being Kurt's Jagstangs and Mustangs crafted by the same luthier (Scott Zimmerman), it would be rather non-sense to have different specifications unless duly requested by Kurt himself, but we established not being the case, as it would have been mentioned from one source or another in the likes of:
"On the next Jagstang's revision I want a neck like Skystang III" or "On Skystang VI I want a Jagstang blue prototype neck", instead we just had Fender's mantra: "it has Kurt's favourite neck" which -if we now consider what I've just stated above- could even being true, aside from the fact that said favourite neck wasn't a copy of his 69 Compstang nor of his main Jaguar but simply and rightously (if that then became the footprint of all the lovely comfy MG 69 RI necks), the neck Scott Zimmerman profiled for both Jagstangs Prototypes and Custom Ordered Mustangs.
Remember this:
Vintage Mustangs had either 22" or 24" neck with an "A" (1.5") or "B" (1 5/8") width at the nut;
All the Japanese Reissue NEVER HAD a proper "A" width nut. There's only the "B" width in the MG 65 RI and, guess what, later on we have the new width that came onwards from the MG 69 RI: the METRIC 40mm always indicated in the instrument specification (1.575" for the Imperialists
). There's also a recap I've found on an old OSG thread:
As you can see, disregarding the MG 65's B width, all the later Mustang have got the same 1.574" unique width and the Jagstang's is pretty much the same, they just probably taken the measurement off a neck with a hair thinner clear coat (Remember manufacturing & environmental tolerance).
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In response to this, AcrylicSuperman stated : "It makes perfect sense. It also makes sense as to why the profiles eventually changed and why the KC Mustang never got that same neck when it was produced, because Scott, while still living in Japan, left Fender to build banjos.
I definitely think Scott deserves credit for creating one of the most popular necks of all time."
It all seems to come full circle even more now, thanks to our fellows courtesy and I guess we're safe to say that in fact even both Prototypes and Production Jagstangs have a common matrix.
Furthermore, and curiously, just like the KC signature Jaguar doesn't have a faithful replica of the original neck, the later official KC Mustangs are not a faithful replica of the standard MG 69 RI as the former is reported being a "B" width nut whilst the latter have the unique 40mm Scott Zimmerman spec'd width Fender Japan used on said 69 RI onwards. Let's reiterate it and keep in mind, we determinated that Kurt's Custom Ordered Mustang were basically stock Mustangs 69 RI, at least, before being notoriously modded to his specs.
Cheers.
