Word Study
free coinage
CIDE DICTIONARY
free coinage,
In the fullest sense, the conversion of bullion (of any specified metal) into legal-tender coins for any person who chooses to bring it to the mint; in a modified sense, such coinage when done at a fixed charge proportionate to the cost of the operation. [Webster 1913 Suppl.]
For further exploring for "free coinage" in Webster Dictionary Online