Bills of exchange were privately issued by banks since the high middles ages in Europe and functioned a lot like dollars when convertability was still a thing. It's only relatively recently that they've been tightly controlled. they weren't in mass use like metal coinage was but they were essential to the re-establishment of long-range trade.
They always finally had to be exchanged to gold. Current dollars have no such peg, hence inflation, "quantitative easing" and other things only possible with fiat money. No king ever dreamed of monetary power like that of FRS.
Even in Roman times currency were debased though. Financial technology has a pretty long history (Money Changes Everything: How Finance Made Civilization Possible, was a pretty cool read on that).
Gold was not mostly used by the aristocracy. Coins for laypeople were things like silver, copper or bronze. People also bartered.
>>"Gold coins can be minted at multiple places, or admitted foreign, because their value is gold by weight."
If the value of the coin come from the gold in it, why mint them instead of using the gold directly?
(imperfect) stamp of quality and amount
Gold was used directly, too, as ingots, and as bullion (check out the gold rush of 1849).
But coins show the insignia of the state (and usually the monarch) that minted it; this is an important symbol, and also a guarantee of purity and weight, at least nominally.
Mass fiat money are no more than 2 centuries old, in most places less than 60 years (see Bretton-Woods). They have to be tightly controled by state.