Article IV, Section 1 of the United States Constitution, known as the "Full Faith and Credit Clause", addresses the duties that states within the United States have to respect the "public acts, records, and judicial proceedings of every other state."
As currency is legal tender/promissory note ... Full Faith and Credit in this case refers to universal acceptance of USD by all states. It also defines that the currency is not based upon any intrinsic or tangible value.
Similar to Bitcoin ... the value of Bitcoin is purely based upon what other will pay for it without regard to collateral or credit/payment/value history of any kind other in and of itself. The value of floating currency has no real/tangible collateral or assets only the "Faith and Credit" of the issuer.