Patina
Etymology
From Latin "patina," "a shallow dish or pan." Italian used the same word for the thin film that formed on the surface of old metal vessels, and from there it generalized to any coating deposited by age. The sense widened again from the physical crust to a figurative one, as in "a patina of respectability."
noun · /puh-TEE-nuh/
The mellow surface sheen or film that age and handling give to an object.
What it names
The green film on old bronze or the soft glow of a worn banister — a single word for the way time itself becomes a finish, and often a mark of value rather than decay.
Example
The dealer refused to polish the candlesticks, insisting their dark patina was exactly what collectors paid for.
Related idea
A patina is prized surface age; verdigris names the specific green copper corrosion that is one form patina can take.