In 1939, having failed after much searching to locate any extant seal of Strongbow, I gave in Historic Heraldry of Britain (Oxford, 1939, pp. 36–7) such particulars as I could of two which have perished, one known by a drawing, the other by a photograph and description. Soon after the book's appearance a letter from Captain R. B. Haselden informed me that what I had been seeking existed in the Huntington Library, namely, a complete and almost perfect seal of Strongbow attached to a charter formerly at Stowe. To the historian, the sigillographer, and the herald alike, this seal is of exceptional interest: to the historian, because it is the only known seal extant of an important historical figure; to the sigillographer, because of the unique design of the counterseal; and to the herald, for its bearing on the early history of one of the two or three oldest heraldic devices.