GRESHAMS LAW, in economics, the name suggested in. 1857 by H. D. Macleod for the principle of currency which may be briefly summarized bad money drives out good.
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I copied the above from an internet link. I've always believed this is the reason why gold coins are tough to find. Of course, you could follow Greshams law and always have a gold coin in you pocket, just not spend it.
Basically, if you had credit, paper, copper, silver and gold as possible forms of currency, you'd spend the bad (credit, paper, copper, silver) first and the last one you would spend is the gold (I guess "bad" means the least intrinsic value and "good" means the most intrinsic value). Which probably explains why gold did not circulate much unless it was the only choice. I have read that in my part of Wisconsin, property had to be bought with gold or silver (NOT no down payment, 125% low interest loans!) and payment made somewhere downtown, like the local courthouse or something like that. So the only time gold would likely "circulate" is in large quantities from a train depot to downtown, or from the "rich" district of future large landowners to downtown.
Maybe the best chance for a gold coin then is "out west" where it circulated or old parks near rich districts where a rich person may have had a gold coin in their pocket.