1878
Bland–Allison
The Treasury must make limited silver purchases and coin them. This is not free coinage at 16 to 1.
The Bland–Allison Act of 1878 required the Treasury to purchase a fixed, limited amount of silver each month and to coin it into dollars. The standard silver dollar, dropped in 1873, was struck again under that duty.
Limited purchases are not free coinage at 16 to 1. Specie payments on greenbacks resume the next year, on 1 January 1879. The dollar is not yet defined as a gold unit in the 1900 statute.