A Monetary Background to Spanish Treasure Hunting?

I have always wondered why Joseph Smith Sr, Joseph Smith Jr and their accomplices were treasure-hunting for Spanish treasures. Now, Rothbard's monetary history of the United States might shed some light on this mystery.

Among the gold coins circulating in America were the French guinea, the Portuguese “joe,” the Spanish doubloon, and Brazilian coins, while silver coins included French crowns and livres. [48-49]

More specifically, Rothbard writes:

By far the leading specie coin circulating in America was the Spanish silver dollar, defined as consisting of 387 grains of pure silver. ... Spanish dollars came into the North American colonies through lucrative trade with the West Indies. The Spanish silver dollar had been the world’s outstanding coin since the early sixteenth century, and was spread partially by dint of the vast silver output of the Spanish colonies in Latin America. More important, however, was that the Spanish dollar, from the sixteenth to the nineteenth century, was relatively the most stable and least debased coin in the Western world.[Fn 2] [49]

And furthermore:

Originally, Congress provided in 1793 that all foreign coins circulating in the United States be legal tender. Indeed, foreign coins have been estimated to form 80 percent of American domestic specie circulation in 1800. Most of the foreign coins were Spanish silver, and while the legal tender privilege was progressively canceled for various foreign coins by 1827, Spanish silver coins continued as legal tender and to predominate in circulation. [p.61]

If Rothbard's assertion is correct, then there is a high likelihood that older treasures, before the introduction of US monies, contained Spanish silver coins.  As the Spanish silver coins fell out of use during the 19^th century, people finding the old coins would have assumed that the hoards themselves were buried by Spaniards.

Literature List 

• Rothbard, Murray N. (2010-10-26). History of Money and Banking in the United States: The Colonial Era to World War II. Ludwig von Mises Institute. Kindle Edition.