Born in Boston and educated there and in France, Samuel Breck (1771-1862) was a major figure in the mercantile, philanthropic, and political life of Philadelphia during the first hald of the nineteenth century. With an interest in historical and literary affairs, Breck was an active member of the Library Company of Philadelphia, the Phialdelphia Athenaeum, the Historical Society of Pennsylvania, and the American Philosophical Society (elected 1838). The Breck Collection is comprised of two manuscripts written by Samuel Breck. The first, "Historical Sketch of the Continental Bills of Credit, from 1775 to 1781, with Specimens Thereof" (1840), includes an essay and 153 specimens of Continental Currency. The second essay, "Recollections of My Acquaintance and Association with Deceased Members of the American Philosophical Society" (1862) includes the 92 year-old Breck's reminiscences of his personal relationships with the nationally and internationally prominent membership of the APS.

An electrical engineer and senior editor for Aviation Week and Space Technology, Philip Klass began investigating UFOs in 1966 after participating in a panel discussion on the subject for the Institute of Electrical and Electronics Engineers (IEEE). From that time forward Klass has investigated UFO sightings in an effort to find a credible prosaic explanation, and became one of the most widely recognized UFO "debunkers." A founding member of the Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP), serving on the Executive Council and the UFO subcommittee, Klass has authored seven books and numerous articles on UFOs, including the Skeptics UFO Newsletter in 1989. In the early 1970s, he became interested in space based weapons, and began collecting material related to the Strategic Defense Initiative (SDI) for a possible book. The Klass Collection relate to his forty-plus years of investigating UFO sightings, and includes correspondence with many of the leading UFOlogists, both pro and con. The collection contains case files, subject files, and correspondence. In addition, Klass' SDI material is included.