hallmark

noun

1. an official mark or stamp indicating a standard of purity, used in marking gold and silver articles assayed by the Goldsmiths’ Company of London; plate mark.
2. any mark or special indication of genuineness, good quality, etc.
3. any distinguishing feature or characteristic: Accuracy is a hallmark of good scholarship.

verb (used with object)

4. to stamp or imprint (something) with a hallmark.

noun

1. British an official series of marks, instituted by statute in 1300, and subsequently modified, stamped by the Guild of Goldsmiths at one of its assay offices on gold, silver, or platinum (since 1975) articles to guarantee purity, date of manufacture, etc
2. a mark or sign of authenticity or excellence
3. an outstanding or distinguishing feature

verb

4. (tr) to stamp with or as if with a hallmark

n.

1721, official stamp of purity in gold and silver articles, from Goldsmiths’ Hall in London, site of the assay office; see hall + mark (n.1). General sense of “mark of quality” first recorded 1864. As a verb from 1773.