A person who professionally evaluates authenticity, quality, or value, especially of art, antiques, or collectibles.
He is famous as an appraiser of artworks.
I had an appraiser examine the value of the pot.
Compound of 鑑定 (appraisal, judgment) and 家 (person, expert). The exact historical derivation is uncertain, but the word follows a common pattern for forming occupational nouns.