The book, MYSTERIES OF TIME AND SPACE, reports a brief but mind-boggling spacetime slip when an artifact from World War II appears 16 years after-the-fact. Hunh. So it’s a Forward to the Future TWIDDER for the shell.
On February 7, 1958 an artillery shell fell from a clear sky over Naples, Italy, and clanged loudly as it struck the street. The shell casing bore the date 1942.
At this point we can but theorize what limbo of Time and Space held that shell immobile for so many years.