A one troy ounce silver trade unit is a privately minted silver piece equal in weight to approximately 1.1 ounces, the equivalent of measurement used in precious metal trade to determine the weight. A silver trade unit should be composed of 99.999 percent silver to be considered fine silver.
A troy ounce is approximately 10 percent larger than a standard ounce measurement. The percentage of silver indicates the purity of the trade unit. The value of the silver trade unit depends on the purity of the silver and the weight of the piece. Investors purchasing trade units from a private mint should check the reputation of the mint to make sure that the units provided are of at least fine silver quality.