Personally, I’d be inclined to describe this coin as an ‘erratic’, similar to the big boulders found where there is no clear source of origin. In the pre-modern world, precious metal / bullion objects or coins were a universal currency regardless of the issuing entity.
In colonial and later times here in this country, a common denomination used in commerce was ‘Pieces of Eight’ which were a Spanish Real that was split into eight pieces. This usage remains part of our language whenever a quarter dollar is slang-referenced as a two-bit value. bullion metals were ALWAYS valued as trading currency because they were weighed by the merchant for value rather than just a face value.
Indeed, one of the most famous men of science, Sir Isaac Newton, was instrumental in cleaning up the mess that England’s coinage had become when he was appointed by Charles II to be Warden then Master of the Royal Mint in London. His job was challenging because after the English Civil War of 1645 and centuries of adulterated coinage & counterfeit, few people trusted the actual value of any coins in circulation.
Yup. Ancient coins (particularly Roman coins, which are remarkably numerous even today) that show up in odd places (India, China, even the Americas and Australia) were probably lost by ancient merchants. The usual rather absurd claim is, the flat-broke hard-working pioneers of the past couple centuries were such avid ancient coin collectors that they carried them on their daily work, and dropped them while trapping and plowing.
The federal gub-mint merely published equivalence tables for various coinage in common circulation rather than minting money. The colonies had issued money (I’ve got a 3 cent piece from one of them around here, uh, somewhere) and during The Revolution a table showing relative values against the CC script. The Articles of Confederation apparently continued this practice. The Constitution reserves minting and currency issues to the feds. The first regular printed money didn’t arrive until 1861. Silver certificates ceased to be printed around the time I was born, and I’ve not seen one floating around in circulation (a fiver) for perhaps 30 years or so. In the 1950s silver dollars were still in circulation, at least around here in The Boonies.
https://www.mycreditunion.gov/financial-resources/history-united-states-currency
https://en.wikipedia.org/wiki/Early_American_currency