The Silver Spanish Mill Dollar- A world currency for years
From the 15th till the 19th century this type of coin was not only used by Spain, but most other countries as it's currency. From Central America to Asia.
Comments
The US Coinage Act of 1792 actually gave the US Dollar a PRECISE measurement of what a Dollar is and in my opinion is still constitutionally binding today. This measurement was taken from the Spanish Mill Dollar and Congress Declared 1 US Dollar to be ""the money of account of the United States shall be expressed in dollars or units … of the value [mass or weight] of a Spanish milled dollar as the same is now current, and to contain three hundred and seventy-one grains and four sixteenth parts of a grain of pure … silver." So 1 Us Dollars equals 371.25 grains of Silver