A paperback copy of The Case for the UFO was sent to the Navy. It had been annotated by apparently 3 people who seemed to have knowledge of UFO's and a secret Navy experiment in invisibility. Jessup himself received 3 letters from a man he believed responsible for the annotated book, Carlos Allende. The Navy had copies of the annotated book printed for study. It had been extremely rare until reprinted by Gray Barker.
Although Jessup had a Master's degree in astronomy he worked most of his time as an automobile-parts salesman and a photographer.
He is mostly known for his pioneering ufological writings and his role in "uncovering" the so-called "Philadelphia Experiment"an alleged military experiment that is said to have been carried out by the U.S. Navy at the Philadelphia Naval Shipyard in Philadelphia, Pennsylvania some time around October 28, 1943. The U.S. Navy destroyer escort USS Eldridge was claimed to be rendered invisible (or "cloaked") to enemy devices.