Q. What are the origins of the Harvard Law School shield that was retired in 2016?

The Harvard Law School shield dates from 1936, when the Harvard Corporation and the Radcliffe Trustees authorized the adoption of twenty-seven arms (representing such academic units of the University as Harvard and Radcliffe Colleges, the graduate schools and the various College Houses) in honor of the Harvard University Tercentennial. The arms on the retired shield of Harvard Law School are those of Isaac Royall, Junior (1719-1781) of Medford, Massachusetts, whose bequest endowed the first professorship of law at Harvard. The earliest known example of the Royall family arms, which display three sheaves of wheat on a shield, appear on a bookplate dating from the 1730s that belonged to Isaac Royall, Senior (1672-1739). 

The best source of information on the various arms of Harvard University can be found in an article, "A Harvard Armory" in the July 1981 issue of the Harvard Library Bulletin (v. 29, no. 3)