hallmark

1. (figurative) A distinguishing characteristic.Examples: "You know what a university is, and a university degree? It is the necessary hallmark of a man who wants to do anything in teaching."; "The inference appears to be that there is some subtle connection between immorality and art, as if the handling of the lewd, or the depicting of it, were in some sort the hallmark of the true artist."; "A man needs only to be careful—and lucky—to live a long time in the Solomons; but he must also be of the right sort. He must have the hall-mark of the inevitable white man stamped upon his soul."figuratively