Have we done any backtracking to the original urban legands that were used to create the story in the first place? I guess it depends what you mean by that. Were it not for the LGF document analysis, it would be plasible if unlikely that someone in 1972 who wanted to create these documents could have done so. The technology existed in 1972 for someone with a cold-type press to produce the overlapping letterforms, superscripts, centering, and other typographical features observed in the memo. I suspect a pantograph lettering machine could also have produced such features.
What did not exist in 1972 were two things:
- Any way of producing these documents which would have been easier than simply dashing off a handwritten note. Even if someone skilled in the crafts could have produced the CYA memo in an hour on a cold-type press or lettering machine, the notion that Killian would have had such expertise, or that he would have taken that sort of time even if he did have the expertise, is absurd.
- Any reason to make various formatting decisions in the memo, including letter spacing, occur exactly as they would with the defaults of a program that was developed decades later. The design of computer typefaces and their letterspacing involves a lot of compromises that would not have been relevant in 1972. Because Times New Roman was not designed to match precisely the spacing of anything that came before it, the probability of a match by chance with anything is pretty remote.
To view things another way, suppose somebody had a photo of the Kennedy assassination and in the background was a blackboard on which could be read a group of six numbers and a group of five. Those numbers by themselves might not prove much at first, except that it would be rather odd for someone to have written out such groups of numbers in the 1960's. Suppose, however, that an examination of Illinois Lottery web site revealed that those were the Lotto and Little Lotto numbers drawn on the 25th anniversary of Kennedy's death. Such a find would absolutely prove the photo to be fake.
Not because it would have been any more difficult for someone to write those particular numbers than any other arbitrary set, but rather because it is far more probable that someone would fake such a photo than that such a 1-in-over-1,000,000,000,000 event would occur.