From the APS website: Hugh McLellan Southgate (September 3, 1871 - October 23, 1940) Washington, D.C., was an important collector and student of the Bureau Issues of the United States. He was a founder and first president of the Philatelic Plate Number Association (1926-1928). He was also the first president and chairman of the board (1930-1940) of its successor, the Bureau Issues Association (now the United States Stamp Society).

“H.M.S.” was among the first researchers to make extensive use of the archival material held by the Bureau of Engraving and Printing. He was prominent in the philatelic activities of the Washington, DC area and in the APS.