Note 196 — Chapter XXII · CURRENCY, BANKING, AND CREDIT

With a dual system of coinage the ratio at the mint must be exactly that of the open market, otherwise the metal which the mint overvalues is the only one which will come in to be coined. If mine-owners who produce silver, for example, can get more gold in exchange for it in the open market than they can get dollars for it at the mint, they will naturally exchange it in the open market. But it is difficult to keep the legal ratio in exact accord with the market value because the latter fluctuates somewhat from year to year.