Don't want to play those "I think you're wrong but I won't say why" games once again, so ...
This isn't a case of that. I've let the person addressed know my objections to his version of U.S. coinage history several times, but the business about the U.S. adopting the “Spanish [coinage] system” down to the quarter-dollar value,
“and the French [coinage] system below” is something that keeps getting repeated around here.
Jefferson and other Americans were voicing a preference for a decimal currency very early on. What contributed to their opinions is open to argument, of course, but there is plenty of reason to believe that their basic interest in things decimal was home-grown.
That the Spanish dollar (or at least the Spanish dollar as it was then circulating in the U.S.) was adopted as the American currency unit, or the fact that Spanish and Mexican silver circulated in parts of the U.S. until the legal tender status of foreign coinage was removed in 1857, is not nearly the same thing (as is often asserted on this forum, most recently just upthread) as the U.S. adopting the “Spanish [coinage] system.” Instead, a slightly underweight Spanish dollar was adopted as the new American dollar, underpinned by a thoroughly un-Spanish system of decimal subunits (and for that matter, overtopped by an un-Spanish decimal “super-unit”).
I see nothing intrinsically Spanish in the cutting of coins into halves and quarters—or should I say “half pennies” and “farthings?” Spanish, sure—when you talk about some of the language use, or when you get below the quarters into individual “bits,” at eight to the 8-reales—but that’s the point, isn’t it? I mean, the U.S. did not adopt a system of 8 subunits. The U.S. did not adopt—as asserted upthread—the “Spanish [coinage] system.” It adopted a home-grown
decimal coinage system, with a unit based on the Spanish dollar as was then circulating in the United States.
As for the choice of the half-dollar and quarter-dollar, and for much of their early use in the U.S., what we’re talking about is not nearly so much “Spanish” as it is
“shortage.” Halving and quartering coins is like halving and quartering anything round—it’s the easiest and most natural division, the practical and human way of cutting things. Halve and quarter, and then halve the quarters. Aha! “Bits.” The American language usage descends from the process as it was applied to Spanish and Mexican “dollars,” but the process itself has roots far deeper. Was the halving and quartering adopted as part of the “Spanish [coinage] system,” or because halving and quartering makes practical sense across the whole range of cutting apart round things, and intuitive good sense beyond?
Anyone who knows anything about Thomas Jefferson knows the answer to that. Jefferson didn’t adopt the half-dollar and the quarter-dollar into his proposal for a coinage system because he wanted to render some sort of homage to the “Spanish system.” No way. He did it because it made practical sense within his own idea of things. (And ditto—maybe double ditto—for Alexander Hamilton later on.)
Jefferson recommended a simple decimal currency system (simpler than Morris’ 1782 decimal system by far) into the Legislature in 1784, and it was a suggestion that immediately gained Washington’s support. In mid-1785, the “Grand Committee” recommended (according to the
Redbook) “...a dollar of silver with fractional coins of the same metal (in denominations of half, quarter, 10th, and 20th parts of a dollar); and copper pieces valued at 1/100 and 1/200 of a dollar.”
Which brings us, once more, to the assertion upthread about the French Revolution completing America’s “Spanish [coinage] system.”
The
Redbook:“Congress gave formal approval to the basic dollar unit and decimal coinage ratio in its resolution of August 8, 1786.” (Nussbaum, in 1957’s
A History of the Dollar, says that the “resolution of August, 1786, dubbed the hundredth part of a dollar a ‘cent’—a Jeffersonian term.”)
The
Redbook:“The Massachusetts cents and half cents struck in 1787 and 1788 were the first official coins in the United States to bear stated values in terms of decimal parts of the dollar unit.”
Of course these are all preliminaries to The Mint Act of (April) 1792, which initiated the current American coinage system. And from what I read, October 1793 is when France adopted its own decimal coinage—on paper, anyway—so why do I keep reading here on the forum of the decimal coinage of Revolutionary France completing the American coinage system? If there was indeed a transfer, don’t the dates involved make it more likely that it was the other way around?
Finally, as for the additional assertion upthread re the 1875 introduction of the American 20-cent piece, and its being “an experiment to shift the border” between the Spanish and the French systems....good one.

v.