[hall.mark] n [Goldsmiths' Hall, London, England, where gold and silver articles were assayed and stamped] (1721) 1 a: an official mark stamped on gold and silver articles in England to attest their purity b: a mark or device placed or stamped on an article of trade to indicate origin, purity, or genuineness
2: a distinguishing characteristic, trait, or feature "the dramatic flourishes which are the ~ of the trial lawyer --Marion K. Sanders"
[2]hallmark vt (1773): to stamp with a hallmark