another name for hallmark (sense 1), hallmark (sense 4)
hallmark in British English
(ˈhɔːlˌmɑːk)
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. (transitive)
to stamp with or as if with a hallmark
Also (for senses 1, 4): platemark
Word origin
C18: named after Goldsmiths' Hall in London, where items were graded and stamped