The proof or trial, by chemical experiments, of the purity or fineness of metals,particularly of the precious metals, gold and silver. A trial of weights and measures by a standard; as by the constituted authorities, clerks of markets, etc. Reg. Orig. 280. A trial or examination of certain commodities, as bread, cloths, etc. Cowell; Blount Assay office. The staff of persons by whom (or the building in which) the process of assaying gold and silver, required by government, inr cidental to maintaining the coinage, is conducted.