I. hall ‧ mark 1 /ˈhɔːlmɑːk $ ˈhɒːlmɑːrk/ BrE AmE noun [countable]
[ Date: 1700-1800 ; Origin: Goldsmiths' Hall in London, England where gold and silver articles were tested and marked ]
1 . an idea, method, or quality that is typical of a particular person or thing
hallmark of
These hotels still offer the sort of service which was the hallmark of the grand days of travel.
The explosion had all the hallmarks of a terrorist attack.
Their performance did not bear the hallmark of European champions.
2 . a mark put on silver, gold, or ↑ platinum that shows the quality of the metal, and where and when it was made
II. hallmark 2 BrE AmE verb [transitive]
to put a hallmark on silver, gold, or ↑ platinum