Someone please refresh my memory about the letter.
Was it the original letter? If so it was typed on a typewriter. As a college student in the fall of 1969, I was part of a group of college students that visited FBI Headquarters. The agent giving us the tour told us that the FBI had at that time every make and model of typewriter produced. Certainly, Dan and company could have compared the letter with a typewriter in FBI storage and proved the case against George W. Bush.
Within hours of the segment, the authenticity of the documents was questioned by posters on Free Republic, a conservative Internet forum, and discussion quickly spread to various weblogs in the blogosphere, principally Little Green Footballs and Power Line.[55] The initial analysis appeared in posts by "Buckhead," a username of Harry W. MacDougald, an Atlanta attorney who had worked for conservative groups such as the Federalist Society and the Southeastern Legal Foundation and who had helped draft the petition to the Arkansas Supreme Court for the disbarment of President Bill Clinton.[56] MacDougald questioned the validity of the documents on the basis of their typography, writing that the memos were "in a proportionally spaced font, probably Palatino or Times New Roman," and alleging that this was an anachronism: "I am saying these documents are forgeries, run through a copier for 15 generations to make them look old. This should be pursued aggressively."
Typewriters cannot proportionately space their fonts. Only a computer does that.