In the world of numismatics, size (in this context, weight) matters. Heads have rolled and the guilty have been jailed or bankrupted for minting gold and silver coins that are a bit south of expected weight. Just ask the assayer and former mayor of Potosi.
It’s a very serious business, and it’s easy to see why. Without the vast stores of gold and silver transported from the New World, Spain never woul
d have become a European colonial superpower. Each quantity of silver or gold mined in the colonial mines around Mexico City, Potosi, Lima, etc. and sent to the mint for smelting and/or coining would have a tax, a fifth (or quinto), charged by the crown and hence referred to as the “king’s fifth.” It all adds up after a while, and the king didn’t appreciate being cheated out of any of his money.
When minting cobs, which are hand struck on planchets without collars, the task of making sure the weight was correct must have been onerous. Note that many cobs have trim marks to cut away some of the material. The weight didn’t have to be exact, but it sure had to be credible.
So, how much should a cob weigh? Of course, it depends on the denomination. The largest denomination was the 8 reales (silver) or 8 escudos (gold). Each was supposed to weigh about 27 grams, with a slight underweight tolerance of perhaps three-tenths of a gram. As for the other denominations, The Practical Book of Cobs tell us:
Practical Book of Cobs, 4th edition
The denominations in gold are 1, 2, 4, and 8 escudos. There is no ½-escudo cob, although the ½ escudo did exist in the later milled coinage. The usual denominations in silver are ½, 1, 2, 4 and 8 reales. (A few ¼ reales were minted in the earliest periods but are generally rare and seldom seen.) Each lower denomination was supposed to weigh exactly one-half of the next larger denomination.
Given that formula, a 4 reales or escudos coin should weigh around 13.5 grams, a 2 reales or escudos coin around 6.75 grams, a 1 real or escudo coin around 3.375 grams, and a ½ real around 1.69 grams. There would be more leeway with silver than gold, which is more precious in any era.
One of the best and cheapest purchases you can make if you’re serious about collecting cobs is a scale, so you can weigh your coins. If you’re concerned about whether a co
in you just bought is genuine, weight it! If it’s significantly underweight, then there’s your red flag. The BIG exception is shipwreck silver coins. Silver corrodes in salt water so many shipwreck cobs are underweight, sometimes significantly. This is not true of gold which comes out of the ocean as intact as the day it went down with the ship.
Of course, you should always deal with a reputable numismatist when buying or selling coins!
Long Beach Expo This Week!
If you’re in southern California, don’t miss an opportunity to meet Dan and Augi at the Expo. See them Wednesday through Friday. They will have inventory for sale and/or can take your consignment for our upcoming Treasure, World and US Coin Auction #19.
SEDWICKCOINS BLOG 
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