This is one of my favorites. It basically says that if I owe the State money, I must pay in gold or silver coin, no substitutes, no gold/silver certificates, just coin. How does it compare to what the FRNs in your pocket read? This note is legal tender for all debts public and private. If that is not a contradiction, I don't know what is.
Import duties were at one time paid in gold and silver coin. Why? Because under the Constitution, there was no alternative. This part of the Constitution monetizes gold and silver by making people pursue it, and not something else such as Federal Reserve Notes, to pay taxes. Has this part of the Constitution ever been repealed? No. So whatever color of law under which the government is operating that lets it accept Federal Reserve money as tender for taxes, is clearly unconstiutional and a crime is being committed every time such tender takes place. So while y'all are busy arguing if secession is ok or not, the crime is happening right now of Americans being forced to use paper money that has no practical difference from the Continental, the Assignat, the Deutchmark of the Weimar Republic. America was supposed to be different from all the other BS nations that suffer from the abuses of paper money. And her difference begins right here with this clause. Why is it while everyone is arguing over whether or not secession (when now 1861? that's a current event) or bibles in the classroom is Constitutional, no one ever seems to take up the cause of this blatant violation? If not for the ability of the government to ignore this part of the Constitution, we would not have the IRS, bloated bureaucracies, tax rates that take 30-40% of your income.
It's not a contradiction at all. Article I, section 10, says that a state may not make anything but gold or silver legal tender (meaning that a state may not pass a law saying that you must accept repayment of a debt in paper money if you're unwilling to accept it). Congress, on the other hand, is not placed under any such restriction; it is authorized in Art I, sec. 8,to "coin Money, [and] regulate the Value thereof," without any mention of gold or silver. Thus, the power to establish paper money was one of those powers (like the power to make treaties, raise armies, etc.) which was given to the federal government but withheld from the states.