"For example, there was a kit for a motorcycle that was never assembled. From 1913."

Jeez, how many visitors to this blog have some project like that? "Yup, been meanin' ta get ta thet..."

A familiar example of this (to mathematicians, anyway) is Ramanujan's "Lost Notebook": briefly, R. died in 1920, leaving a thick sheaf of manuscript papers put in the hands of G.N. Watson for scrutiny, editing, and, ultimately, publication; it was recovered from a pile on the floor of Watson's flat a couple years after his death in 1965; and at least edited and published within the last six years...