Free Coinage

Under both the gold standard and the silver standard, people could take either metal to the mint and receive in exchange coins of equal weight at no cost. In practice, if either metal were slightly under-valued, they would take that metal for minting and sell the other in the market.
In Britain, for example, gold was slightly under-valued after the 1696 recoinage and thereafter was taken to the mint for coin, while more highly valued silver was sold as bars for export to the East. By comparison, in the early years of American independence, silver was slightly under-valued and so it was taken to the mint. In the one case Britain got a gold coinage and in the other the United States a silver coinage forming the main circulation.

Free silver coinage ceased once countries switched to the gold standard and free gold coinage was also generally suspended in 1914 at the outbreak of World War I.