A scaled and dimensioned drawing of the Presidential Seal, as attached to Executive Order 10823, May 1959 (courtesy Smithsonian Institution and Wikimedia Commons).
The following OAH Distinguished Lecturers specialize in presidential history.
Peter S. Onuf
Robert H. Smith International Center for Jefferson Studies, Monticello and University of Virginia (Emeritus)
Donna C. Schuele
California State University, Los Angeles and UCLA Center for the Study of Women
Robert Brent Toplin
University of North Carolina at Wilmington (Emeritus) and University of Virginia