What's more interesting is that a third of these plates were destroyed by Donald Howard Menzel without reason or explanation.

From Wikipedia: "During World War II, Menzel was commissioned as a lieutenant commander in the United States Navy and asked to head a division of intelligence, where he used his many-sided talents, including deciphering enemy codes. Even until 1955, he worked with the Navy improving radio-wave propagation by tracking the Sun's emissions and studying the effect of the aurora on radio propagation for the Department of Defense.[3][4] Returning to Harvard after the war, he was appointed acting director of the Harvard Observatory in 1952, and was the full director from 1954 to 1966. His colleague Dr. Dorrit Hoffleit recalls one of his first actions in the position was asking his secretary to destroy a third of the plates sight unseen, resulting in their permanent loss from the record."