The first-gen tort guards did have thicknesses that were all over the place, and there is shrinkage over the years as well, complicating things. There were also weird situations sometimes, like only w/b layers under the tort. Variation was the norm. But in '64, when they switched to laminating the tort over more stable w/b/w layers, the middle layer was far more consistently thin. Therefore first gen guards are generally thought of as having a thicker black layer (though not necessarily "thick"), while second-gen ones are generally thought of as having a very thin black layer.
It would only be something that would blip on ones radar until the pots and/or body date were checked out. Those things being in order would put one more at ease. As would seeing the guard in person, which would make the material used for the white and black layers plain as day (hard to show in photos).
To me, that darkness around the edge looks more like the artifacts of an amateur refin than the original finish. Plus it makes no sense that everything on the bass would have been taken down to the point at which the original sealer was chemically stripped (evident by the wood grains being clear of sealer). Perhaps I am reading the photos wrong (it's hard to tell from pix), but it looks like that dark stuff is directly over the ash grain, sinking quite a bit into it in places. The pre-Fullerplast finishes were exceptionally easy to chemically remove all the way down to the wood. There's no reason someone would do so on 98 percent of the body only. The ash grain was stripped of its filler, which you don't do by shallowly sanding, only with chemicals. Personally, without having the bass in hand, my gut says it was stripped twice, then clear coated like it is now.
Is the dark area dark brown, or black?