Although it is commonly used as “A is the hallmark of B”, to describe the distinguishing feature of an entity, I was surprised to learn that a hallmark is
an official mark or stamp indicating a standard of purity, used in marking gold and silver articles assayed by the Goldsmiths’ Company of London (1)
It can also be used as a verb, but its noun variant is more common. A google search yielded the following:
“The hallmark of aristocracy is responsibility”
“Humility is not the hallmark of poets”
“Good manners are the hallmark of a lady”
“Verbal Behavior as the hallmark of intelligence”
I’m unsure that this word is employed properly in these examples.
References:
