But the principle of national sovereignty which operates in Congressional legislation on money, currency, coinage, and legal tenders, does not nullify the principle of contracts. A lawful contract between parties that calls for payment of a particular article with a particular article, be it silver coin, gold coin, national bank notes, treasury notes, reserve bank issues, or subsidiary coin, is satisfied only when executed in the terms of the contract. The obligation of the contract would be impaired if it were executed otherwise than as the contract itself sets forth.[72] 31. Congress is not under contract to coin money, to pay the debts of the United States, or to borrow money in any particular way. Duties, excises, and imports must be _uniform_ throughout the United States, and this condition is a fundamental limitation. No limitation is placed by the Constitution on the power of Congress over the currency. This power is supreme. It is a power which, duly exercised, secures the existence of sovereignty itself.[73] A function of sovereignty is performed in the issuing of a bill of credit, the sovereign power thus pledging its faith, and the thing issued is designed to circulate as money. The State, or Commonwealth, in the Union, is not a sovereign for this purpose, as the Constitution provides.[74] So when a State incorporates a bank, which issues bills of credit, the act of the bank is not an act of sovereignty, and the State, though a stockholder in the bank, imparts none of its sovereignty to the bank. The bank as a corporation, not the State as an incorporator, is answerable for the obligations of the bank.[75] To constitute a “bill of credit,” in the meaning of the Constitution, it must be issued by a State, on the faith of the State and be designed to circulate as money.[76] 32. Power to provide for the punishment of counterfeiting the securities and current coin of the United States is specially delegated to Congress,[77] but it is not denied to the several States. The power to coin money belongs exclusively to Congress[78] as a mark and necessary incident of sovereignty, but counterfeiting the coin constitutes an offense against both the State and the United States. The uttering of counterfeit coin is a cheat, and the State can protect its citizens against fraud by exercise of its police power. Such offenses fall strictly within State jurisdiction. Counterfeiting debases the coin, throws spurious and base metal, or false securities into circulation, and is an offense against that constitutional power which is exclusively authorized to create a currency for public uses. The offense is against the sovereignty of the nation, and, being a fraud, it is against the sovereignty of the State. In either case it imperils sovereignty.[79]