Assay Balances

Assay balances were used for one of two purposes: Either the determination of the content of a precious metal (usually gold) in an alloy, thus establishing the fineness of the latter (usually in carats or per cent). Or the determination of metal content (usually in per cent) in an ore. Both these processes come under the name of assaying, and the balances were mostly found in assay offices, national banks, metal processors and mining laboratories. They normally have a very small maximum load (commonly 5 grams) and high resolution (commonly 5 ... 1 micrograms). For this reason the more modern assay balances are closely related to microbalances. In terms of balance design they are fairly basic, often lacking damping mechanisms and optical projection, achieving their performance purely by careful design and very fine manufacture and adjustment. The shape of their pans and suspension wires is typical for this application and not seen outside this field.

Model SA1 assay balance, 5 g capacity, 0.005 mg resolution, weight loaded to 0.1 g, additional rider. Stanton assay balances are relatively rare. They are based on the MC series, using the same beam and case.
A much older long-beam assay balance (late 19th century) is shown in the Oertling slideshow