Light-blue ribbon identified the wearer as a delegate at the18th Convention of the National Association of Letter Carriers (NALC) held in Rochester, New York, from September 4-9, 1911. The suspended medal includes the NALC’s distinctive symbol, adopted in 1891, of a hand holding a stamped letter addressed “U.S.A” that is encircled by the union’s name.
Letter carriers were the first postal workers to form a union. The NALC was founded to represent city delivery letter carriers on August 30, 1889, in Milwaukee, Wisconsin.
http://www.nalc.org/nalc/facthist/index.html (Accessed April 11, 2006)