Paper money, at least in America (and I believe this is inherent in the definition) is described as “notes” – meaning that the government is signing this certificate of its indebtedness to you for the face value of the note, just as (in theory at least) you can go talk to your friendly banker and sign a note acknowledging your indebtedness to the bank, in return for which signature he gives you money – expecting to collect it back, with interest, when the note becomes due.
I’m too lazy to Google out the statistics, but something like 99% of all present U.S. currency is in Federal Reserve Notes – notes issued by the Federal Reserve Banks to serve as currency. A small fraction are United States Notes, issued in $5 and $100 denominations (and I think they’ve been discontinued as new issues) in which the U.S. Treasury and not the FRB is the issuer. And a vanishingly small percentage are silver and gold certificates in the hands of collectors.
When I was a kid, something like 20% of the circulating currency was silver certificates, but for reasons that will become obvious, neither public nor private sectors wanted them to stay in circulation.
What’s a silver certificate, or for that matter a gold certificate? Well, if currency is notes the same as your note to the bank (or an IOU for that matter), it involves a promise to repay. What does the government promise to repay? The face value of the note in – more money! But it itself is legal tender, the standard of currency. So in one sense the notes back themselves, and in another, the sole thing backing them is the credit of the United States as a nation – by using Federal Reserve notes, you are accepting the idea that the U.S. government is going to be around and functioning, and honoring its debts, for the foreseeable future – a reasonable assumption for the U.S., but not so reasonable for the People’s Republic of Coupsylvania – whoops! I mean the Etat de Coupsylvania – whoops! – the Interim Military Government of the Democratic Republic of Coupsylvania…
However, a silver certificate was a $1 bill, or a $5 or $10 or whatever, for which the United States solemnly promised that on demand they would give you $1, $5, or $10 worth of silver, which was a fixed weight of silver metal, a fraction of an ounce. Likewise, before 1935 or so, the country had gold certificates where it promised to give that amount of gold to you on demand.
Well, there were three problems with this. First, this bound the government to hold a given amount of silver or gold in reserve to guarantee that it would be able to redeem its certificates, something that tied its hands figuratively in terms of money management. Second, Gresham’s Law applied – “bad money drives out good” – because which would you rather hang on to, a secured note that you can take to court and take ownership of the collateral if the debtor defaults, or an unsecured note where his word is your sole guarantee? So people sat on and hoarded the secured certificates and got rid of – spent – the unsecured notes, effectively reducing the money supply. Third, by tying the value of a piece of currency to a fixed quantity of precious metal, the silver and gold certificates had a deflating effect on the currency. Plagued over the last 65 years by inflation, that sounds good – except that deflation is associated with recessions and depressions, which are Not Good Things.
I would have to see the specifics of the proposal, but even if a small fraction of American money is tied to a precious metal, and there’s some effective way to keep it from vanishing from the marketplace through hoarding, that fixes the value of money relative to gold – hence, the gold standard – because a $20 bill is a $20 bill, worth $20 at today’s prices, whether it’s secured by Olveta Culp Hobby’s signature or 0.002 oz. of gold in Fort Knox.