The Silver based United States Dollar was in use for 175 years (from 1789 to 1964).
Name me one "Fiat currency" issued by a government which was first introduced prior to 1836 (175 years ago) and is still in use today.
I see no "currencies issued by governments debt free" which have worked as well as the good old United States Dollar that was in use when I was born (yeah, I was born before 1964).
Also, I beleive that the constitution specifies that "money" should be gold and silver coins. No place in Article 1 Section 8 is Congress given the power to declare anything "tender in payment of debts" and the states, while they retain that power, are prevented from making anything but Gold or Silver coin "Tender in Payment of debts. That's in Article 1, Section 10 of the Constitution.
I was born before 1964 as well, but "the good old United States Dollar that was in use when [you and I] were born" came to a crashing halt in 1971 in what was known as the "Nixon Shock". That's when Government-manufactured budget and trade deficits caused a run on the dollar which depleted our nation's gold reserves. It seems that backing a currency with gold works, as long as it can never actually be redeemed, which makes it essentially fiat money anyway.
I think the silver dollar worked well and I have nothing against it, but like gold, silver has limited supply so wealth will tend to concentrate in the hands of a few. The Romans were successful with fiat currency until Ceasar replaced it with Gold. The British were also successful with tallies from 1100 AD through 1694 AD, when the Bank of England was formed. We have flipped back and forth so many times since the beginning of the Replublic, as have other nations, that there is not a standard in existence today which existed pre-1836. Except for maybe the Dutch guilder, which is still accepted as currency until 01/01/2032, but even it has been flipped numerous times due to war and conquest.
Federal Reserve notes became our legal tender under the Federal Reserve Act, which snuck its way through Congress on Christmas Eve 1913. However, from 1934 to 1971, the period you referred to, only foreign holders of Federal Reserve Notes could exchange them for gold on demand, not U.S. Citizens. Interesting!
History proves that it's not what backs a currency that matters, it's who controls its quantity. And unfortunately for us, control of our currency is exclusively in the hands of private bankers, and not our representative government. That's the problem as I see it. And I'm not alone. Capitalism depends on the availability of capital. But no one ever said it had to be issued by the government through debt.