Need Help Authenticating 1785 MO Fm 8 Reales

Don't know anything about the old coinage but you have a great camera.Wanna trade? HarHar

jgenn You are asking a really difficult question to answer simply.

The simple answer is that most real 8Rs will have an actual SG rather NEAR the "technical" value for 0.903 fine silver. The range I have observed having tested at least 1,000 "real" coins is 10.25 to 10.38. The range tends to be wider on the low side than on the high side. There can be some cases of "real" 8Rs outside this range but most on closer inspection have extenuating factors. By this I mean that there are many reasons for slight variations in SG. For example, gold as a trace contaminant did occur in amounts as high as 0.8%. There were times before the advent of mercury extraction methods when gold traces were simply left in the silver. This adds to the SG. Air can also get trapped in the ingots (as can other extraneous items) which results in a lower SG. Then there is surface dirt - oil and material clinging to the coin in protected areas. Most of these factors tend to lower the SG (slightly).

When looking for a forgery, most are going to be far wide of the mark - 9.9 to 10.1 is a very common range for early forgeries but far lower densities occur after the advent of German Silver in the 1840's.

The numbers you have look fine to me 10.36 is getting up there but woul not make me say "this is fake."

The silver forgeries made for the China trade in the 1890s will usually be a bit higher (10.4 or so). I have seen 0.999 fine silver used in a very few instances. There I suspect the reason was that blanks were make from ounce rounds.

Another thing to consider are historical reports that some branch mint facilities produced "sub-standard" coins with the correct dies. These will normally run under 10.2. They were 0.600 to 0.800 fine and the alloy varies with odd mixes of trace elements.

Does anybody know about a book dealing
just about 8 Reales? Looks like a complex and fascinating field.