Value of Spanish silver dollar and British pound during the Pirate Age? Part 1 of 2

Spanish Pillar Dollar, Piece of Eight, Charles IV of Spain 1803 a by Jerry “Woody” is licensed under CC BY-SA 2.0

The Spanish silver dollar is referred to as the first global currency. There were so many produced and they  spread so far across the world that they were the common currency.

Because the Spanish silver dollar was present everywhere and the valuations referred to during the pirate are in British pounds, let’s explore the value of each.

Spanish silver dollar

Several things I’ve read said the coin was held at constant amount of currency for centuries. This is unusual because rulers usually start debasing their currency in an effort to stretch their resources by conning the people.

The Spanish silver dollar was about 1.5 inches in diameter.

Wikipedia says it was minted with a consistent content from 1497 through 1728. It contained 25.563 grams of pure silver at 0.9306 fineness, or 93.06% purity.

It was set at 8.375 coins to the Castilian mark of silver which was 230.0465 grams.

That would be .902 ounces of pure silver per coin and 8.115 ounces per mark.

The Morgan Dollar by James Capp  is licensed under CC BY-ND 2.0

For contrast, US Morgan (1878-1921) and Peace dollars (minted 1921-1935) are 90% silver with .7734 ounces of pure silver.

If you need a rough physical illustration of a Spanish silver dollar, imagine the time you held a Morgan or Peace dollar.

British pound

Details from the era of Queen Elizabeth, who ruled from 1533 to 1603, provide context for the pound during the Pirate Age.

The British pound (£) was set at 20 shillings (s). Each shilling was set at 12 pence (d, for Roman denarius – don’t ask, I haven’t looked for the reason). So there are 240 pence to a pound and 20 shillings to a pound.

With only an hour or so of searching on the web it is difficult to find the silver content of British coins in the 1600 timeframe.

Here is what I’ve learned. If this misses the point or someone can give me better enlightenment, please do so.

Coins of the pound sterling article by Wikipedia says the British penny was set at 22.5 Troy grains, or 1.458 g. It was designated by Fiat to contain 24 troy grains (1.56 g) to approximate the premium for being minted into a standard coin.

A pound, referred to as tower pound, was set to equal 240 of those coins. Therefore the tower pound had 5400 grains, or 349.91 g, or 12.34 ounces.

Purity of the coins was set at 92.5% silver, which is called sterling silver, and 1158. The concert was debased, eventually driving to one third. Wikipedia says during Edward VI reign (1537 – 1553) the sterling standard (92.5%) was reinstated. That. That purity level was maintained until 1920, according to the article.

So, as best as I can figure out (which probably is wrong for some reason) that would put a British pound at about 5400 grains / 350 grams / 12.3 ounces.  Whether that is the actual silver content or before adjusting for 92.5% purity I do not know. The level of uncertainty surrounding my research leads me to ignore the distinction between sterling and 100% pure.

I shall proceed on the basis that a full British pound at the time of the pirate era in the American colonies was 350 grains grams/12.3 ounces pure silver.

That gives us the following relationships:

  • Spanish silver dollar – 25.56 grams pure silver or .902 ounces
  • British pound –  349.9 grams /12.34 ounces pure silver.
  • The ratio is then 13.69 Spanish silver dollars equal 1 British pound 13.69 British pounds to the Spanish silver dollar. (Oops – got the relationship reversed).

Part 2

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