Workshop: National 50s Adjustable Neck Gizmo

I've finished up this guitar since these pics but, oh my, I wanted to share the coolest neck-adjustment gizmo ever invented. I'm surprised these didn't stay in normal use as it makes the need for neck sets irrelevant and... tone is still great.

Above you can see the adjustment mechanism with 4 Allen-adjusted screws. The two up near the neck itself adjust back-angle and left/right alignment at the top of the neck block area. The one on the bottom sets overall back-angle of the neck. The middle (largest) adjusts overall tension up to the neck block which "locks" your settings in place. It was a breeze to dial in perfect back angle and set it up so that the fretboard extension rose peacefully over the top without bumping "up" under tension. The other benefit is the neck runs all the way right to the body with no extra overhang from the heel area except for a plastic cover (and thus, fret access is improved).

The other surprise is a shockingly-large steel non-adjustable "truss rod" reinforcement. It's almost the entire width of the neck. I'm guessing this bit runs all the way to the adjustable gizmo in the heel and I'm also guessing it's the reason there are no dead spots when playing up and down the neck and also why the neck is perfectly straight even though it's thin for the time and rocking a set of 12s.

This neck system is the type seen on National-branded guitars using a National neck and Gibson body (like the Nat'l 1145 archtop seen here or the Nat'l 1155 jumbo flattop guitars).