Excerpt from the web site that you cited:
“Highlighters and fine-line markers were first seen in the 1970’s. Permanent markers also became available around this time. Superfine-points and dry erase markers gained popularity in the 1990’s.
The modern fiber tip pen was invented by Yukio Horie of the Tokyo Stationery Company, Japan in 1962. The Avery Dennison Corporation trademarked Hi-Liter® and Marks-A-Lot® in the early ‘90s. The Hi-Liter® pen, commonly known as a highlighter, is a marking pen which overlays a printed word with a transparent color leaving it legible and emphasized.”
A signature as seen on the Obama COLB would have had to be done with a “fine-tip” marker.
That's still a year after the miraculous birth. Just because Horie invented a fiber tip pen doesn't mean it was patented and mass produced in '62. It was not until about '78 that the Bic felt tip super fine pen was popular. I know this because my college bf gave me a dozen boxes of them for Christmas because I thought they were the neatest new things on the market. It was amazing how easily it glided across paper and it seemed you could write faster. Before that, everyone used ball point pens. Highlighters were just beginning to be popular then, too.
Yes, there were felt tipped markers before that but they were big fat things that were used to write on cardboard - mainly moving boxes. And they didn't come in more more than black, red, and maybe blue and green.
No, artists found such pens around ~ legitimate or not.
Really, back in the more recent Dark Ages, people made do with what they had. When it comes to penmanship all of them wrote much better than we do today (I've given up handwriting myself ~ just don't do it anymore) ~ and they sought to leave a handsome line ~ and could do it quite artistically.
How that sort of work "scans" may yield an artifact that was not intended by the designers of the scanning system.