Hi GGJaguar many thanks for your response.
Regarding the first point, then I'm happy to have a JF65-12 because I love the thick neck and guess that two truss rods make an stronger neck than one. The lighter bracing must be amazing because I cannot imagine a 12 string louder than mine!! haha...
HI Kenneth, welcome aboard!
I'm a little late to the party, but wanted to point out that the true purpose of the dual truss rods was to compensate for the large difference in string tension between the bass and treble sides of the neck, which in turn affect fretboard alignment and thus intonation. They allowed fine adjustment on each side of the neck: a little tighter for bass, a little slacker for treble. We've even seen cases where mis-adjustment of the rods by folks who didn't realize that concept fractured the neck.
So in conclusion I guess that there are no differences in the main point, the woods: solid sitka spruce top with laminated maple arched back (I don't know if sides are solid or laminate maple).
Yeah the basic formula is the same. Sure they did help make a stronger neck that resisted the twisting force caused by the unequal string tension, and the 3-piece necks also help in that regard.
The differences are subtle but according to Guild's website the current F512M has adirondack spruce bracing, which wasn't used in Westerly as far as we know (first "officially" spec'd by Guild in Tacoma). Adi is stronger than sitka by weight, so it allows lighter bracing to be used for the tops, letting 'em resonate more. Explains why they could be as loud if not louder than a late Westerly build.
Still, late Westerly guitars have a reputation for excellence and I'm sure if you put yours up against a new one in a blind listening test, the judges'd be split 50/50.
According to my notes the Guild F-412 was re-named the JF-65M-12 in 1987 during the Westerly period and changed back to F-412 in 2002 in the Fender Corona period./QUOTE]
Cordoba Guild have decided to now call it the F-512M.
I wish they'd just stuck with F-412.
HI Bruce, that "JF65
M-12" designation didn't last long, in fact I think it may be one of those model number anomalies that were common in that period when Gruhn implemented his new model number system. It only shows for that year in the s/n lists, by way of cross-checking. In any case, by '90 it was just the JF65-12.