Discussion in 'World Coins' started by Volante, Oct 31, 2013.
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That said, the specific time period being discussed also has a bearing. For example, during the cob period coins always had an established minimum & maximum weight tolerance, and a fineness, but the very nature of the coins led to clipping which was a pervasive practice. As a result of this the weight of surviving coins is all over the map and the weight is almost never used to determine authenticity, because it cannot be.
With the advent of the milled coinage in 1732 things changed. Milled coinage put an end to clipping, so the weight can be used to determine authenticity. With milled coinage the maximum permissible weight for an 8 reales was 27.2638 grams. The minimum was 26.8646 grams. That is a very strict tolerance level and yes they did indeed use 4 decimal places. And these tolerance levels applied to all mints.
Now contrary to what a lot of people think loss of weight due to wear is almost a non issue. That is because there is no appreciable loss of weight due to wear until you get to very low grades like VG. Even coins in F have no appreciable loss of weight.
There is however the issue of deliberate underweight coins with coins from Potosi and from a specific time period. These coins were deliberately minted and struck underweight by mint officials. And they were caught, and some were executed, others were punished in other ways. But the underweight coins still exist.
So short and sweet, in some cases weight can be used to determine authenticity and in some cases it cannot be used. And you have to know all of this information to know which is which.
What I listed above was for 8 reales coins.
That maybe what is listed in the book you reference. But the numbers I listed above are what is listed in the Royal Decrees that still exist in the Spanish archives today.
I ordered this book, but based on this little tidbit I will read it with a skeptical mindset.
It is absolutely correct to say that a milled, non shipwreck, 8 reales coin should not be below 25 or 26 grams - even in low grades.
However, there are other considerations. Shipwrecked 8 reales coins, which are fully certified and sold by reputable dealers, are regularly sold at weights as low as 20 grams - in both milled and cob varieties.
There is also the issue of the Potosi mint in the 1600s, where 8 reales were debased by reducing silver content and clipping. Most of these coins were tracked down and destroyed, but many also survived.
So if your coin is milled, and looks complete, it should be 26 - 27 grams. If it's not milled, and/or is a shipwreck coin, the minimum weight can be much much lower.
ps Linked thread https://www.cointalk.com/threads/8-reales-spanish-empire-and-peninsulars-for-all.258294/page-4
Weight: 26,77 g
Sum before normalization: 102.8 %
Normalised to: 100.0 %
1 Ag 92.58
2 Cu 2.81
3 Cl 2.27
4 Na 0.95
5 Ca 0.40
6 Si 0.38
7 S 0.21
8 K 0.13
9 Al 0.12
10 Pb 0.09
11 Mg 0.05
12 P 0.02
Separate names with a comma.