The
Society of Antiquaries has two societies to which Fellows may
belong. The older of these is the Cocked Hat Club (founded 1852), and
the younger (founded 1907) the Essay Club.
The Essay Club got its name from the initial letters "SA" for "Society
of Antiquaries". (From “A History of the Society of Antiquaries”, by
Dame Joan Evans, first woman president of the society 1959 - 1964.)
www.wikipedia.org/wiki/Society_of_Antiquaries_of_London