What date is associated with e that is reminiscent of its first appearance in written form 100 years earlier?
Exactly! However, I was just looking for 1828. "...two hundred...? Quoting Wikipedia e (mathematical constant):
"The first known use of the constant, represented by the letter b, was in correspondence from Gottfried Leibniz to Christiaan Huygens in 1690 and 1691. Leonhard Euler started to use the letter e for the constant in 1727 or 1728,[4] and the first use of e in a publication was Euler's Mechanica (1736). While in the subsequent years some researchers used the letter c, e was more common and eventually became the standard."