Any commodity which is generally acceptable in exchange is money. Money has been developed through the needs of commerce and not on account of the sanction of the government. Where the government reinforces the general acceptability of money by providing by law that the money in question must be accepted in the payment of debts, the money becomes a legal tender. In the United States gold coin is legal tender for all debts, public and private; silver dollars are legal tender where the contract does not provide otherwise; subsidiary silver coins are legal tender to the amount of ten dollars in one payment; the treasury notes of 1890 are legal tender except where the contract provides otherwise; United States notes are legal tender for all debts, public and private, except duties on imports and interest on the public debt; the nickel and copper coins are legal tender to the extent of 25 cents; gold and silver certificates and the different forms of bank notes are not legal tender.