That restricts the various states from having their own money systems (thankfully!). It doesnt at all lay out what kind of money system we should have nationally.
James Madison, Federalist, no. 44, 299--302
The right of coining money, which is here taken from the States, was left in their hands by the confederation as a concurrent right with that of Congress, under an exception in favor of the exclusive right of Congress to regulate the alloy and value. In this instance also the new provision is an improvement on the old.
Whilst the alloy and value depended on the general authority, a right of coinage in the particular States could have no other effect than to multiply expensive mints, and diversify the forms and weights of the circulating pieces. The latter inconveniency defeats one purpose for which the power was originally submitted to the foederal head. And as far as the former might prevent an inconvenient remittance of gold and silver to the central mint for recoinage, the end can be as well attained, by local mints established under the general authority.
The extension of the prohibition to bills of credit must give pleasure to every citizen in proportion to his love of justice, and his knowledge of the true springs of public prosperity. The loss which America has sustained since the peace, from
the pestilent effects of paper money, on the necessary confidence between man and man; on the necessary confidence in the public councils; on the industry and morals of the people, and on the character of Republican Government, constitutes an enormous debt against the States chargeable with this unadvised measure, which must long remain unsatisfied; or rather an accumulation of guilt, which can be expiated no otherwise than by a voluntary sacrifice on the altar of justice, of the power which has been the instrument of it. In addition to these persuasive considerations, it may be observed that the same reasons which shew the necessity of denying to the States the power of regulating coin, prove with equal force that they ought not to be at liberty to substitute a paper medium in the place of coin. Had every State a right to regulate the value of its coin, there might be as many different currencies as States; and thus the intercourse among them would be impeded; retrospective alterations in its value might be made, and thus the citizens of other States be injured; and animosities be kindled among the States themselves. The subjects of foreign powers might suffer from the same cause, and hence the Union be discredited and embroiled by the indiscretion of a single member. No one of these mischiefs is less incident to a power in the States to emit paper money than to coin gold or silver. The power to make any thing but gold and silver a tender in payment of debts, is withdrawn from the States, on the same principle with that of striking of paper currency.
"Of all the contrivances for cheating the laboring classes of mankind, none has been more effective than that which deludes them with paper money." -- Daniel Webster
"The constitution, therefore, considers the emission of bills of credit [printing of paper money], and the enactment of tender laws, as distinct operations ... Both are forbidden." -- U.S. Supreme Court, Craig v. Missouri, 4 Peters 410
