Short version of the question: How do I determine the value of "40,0000 Spanish Dollars" in U.S.D in 1816?
Long version: I am writing a dissertation on maritime piracy in the early nineteenth century U.S. A ship pirated in one of my case studies--the schooner Plattsburg(h)--is said to have carried 40,000 "dollars" at the time she was attacked, but what "dollars" means ambiguous.
In a transcript of the trial, published by a commercial press immediately after the trial, the owner of the ship, Isaac McKim, says that the ship carried "forty-one to forty-two thousand dollars in gold and silver." I had assumed, upon first reading the transcript, that this meant "forty-one thousand U.S. dollars in gold and silver."
I was later reading some diplomatic correspondence concerning the extradition of the accused pirates from Europe to the U.S. Multiple authors referred to the cargo as "40,000 Spanish dollars," which I take to mean 8-real coins.
Now, determining the actual value of the cargo is immaterial to my argument, but I wanted to mention the ambiguity in a footnote and describe what the different values would be relative to each other depending on how one interpreted "dollars." So essentially I'm looking for a currency exchange list for USD to 8-real coins in 1816. After searching on Google/Scholar for a bit, I've turned up nothing useful. Any suggestions on where I might begin?
So early 1800s is kind of tricky because it was before the classical gold standard period when Exchange Rates were fixed and thus data much easier to discover.
But both the US and the Spanish used precious metals to mint coins, so the way I would do it is find the silver content of 8-real coins, the gold content of US dollar of the time (I believe pieces of data would be much easier to find), and then simply take a look at the ratio of gold:silver exchange (which I believe was fixed at the time in the US at least) to calculate the value ratio between the two coins.
Does this sound good?