The Oxford Thesaurus An A-Z Dictionary of Synonyms - hallmarkn.

1) authentication, verification, seal or stamp (of authenticity or approval) , mark, device, sign, symbol; plate-mark; assay-mark: From this hallmark we know when and where the piece was made, by whom, and its degree of purity. Surprise endings are the hallmark of O. Henry's short stories. 2) feature, stamp, mark, earmark, trade mark, characteristic, identification: From his hallmark, a tiny axe, you can tell that the painting is a genuine Fellworthy.