This concerns the 19th century Mexican 8 Reales (also including the continuing Un Peso type of 1898-1909). How consistent do you find the actual weight of these to be? Nominally they're supposed be 27.07 grams, but I find that put on the scale, ones I have tend to be around 26.8 or even 26.7 grams, and these are not markedly worn examples. Diameter doesn't seem uniform, either. I haven't examined enough of these to form an opinion on how endemic such shortfalls might be, nor as to whether the products of certain mints are more prone than others to coming in a little small and/or light. I've checked more of the later Un Peso from 1918 to 1945, and they appear to be much more in line with their official specifications.
Well, the early 19th century had some 8 realies minted in Mexico City coming out @ 27.0674 grams. Outside of that they are supposed to all be 27.07 Grams. If the loss can not be explained from wear, then perhaps a counterfeit.
That'd be my worry except that this seems to be the case with more than one of mine. They just don't seem uniform to the same degree that U.S. silver dollars were. A cause for this could also be poor production controls or excessive tolerances, or even corruption in the oversight of the branch mints. A tiny bit held back from each coin struck could make someone very rich, or maybe the purity as attested to by the assayer(s) isn't what it's supposed to be either, with the same result.
Follow-up Here's a small sampling of what I'm talking about. I've weighed these in grains for a little better accuracy (the specified weight of 27.073 grams converts to 417.8 grains). 1898 Cn 414 grains 39.26 mm diameter 1895 Zs 416 grains 39.56mm diameter 1877 Mo 412 grains 39.28mm diameter 1838 Zs 422 grains 37.80mm diameter* * This is a rough average as the coin is not perfectly round. Furthermore, although it has the highest weight, it is also shows the most wear and is notably deficient in size. Even though none of the later coins dip below 39mm in diameter, there's still some variance in this measurement.
I was going to respond initially that I think its more of a mint thing. Remember Mexico had a tremendous amount of mints, and many weren't really being operated in the best interest of the entire country. I know China in the 19th century had lots of the same problems with their branch mints. Its an interesting subject, and one I am sure experts have looked at and researched. I have read about the issues in China during this period, but unfortunately have not read about Mexico in depth for the same time period. I have Grove, do you think that may cover this issue?
http://www.cointalk.com/t168457/ This old thread of mine discusses some of the weight issues. I believe the branch mint weights are well documented in some specialty books but I do not have one in my library. Post some photos when you can. :thumb:
Our CT member Eduard recommended Frank Gilboy’s book on Pillar Coinage. It supposedly contains in depth information on this coin's weight possibly as a function of the mint that produced it & the amount of wear.
Revised & Additional Data I realized I'd made an error in measuring the diameters posted earlier in this thread, so the first four below represent corrections in that regard. The following six are new entries. For those examples that are a bit oblong rather than round, I've given the range of measurements. 1895 Zs 416 grains 39.4-39.5 mm 1877 Mo 412 grains 38.6 mm 1898 Cn 414 grains 38.7 mm 1838 Zs 422 grains 37.7-38.0 mm 1876 Go 420 grains 39.0 mm 1896 Mo 416 grains 38.6 mm 1903 Cn 416 grains 38.9-39.0 mm 1879 Ho 414 grains 39.2 mm 1894 Ho 412 grains 39.3-39.4 mm 1902 Zs 418 grains 39.4-39.6 mm
A few more for the record 1894 Ho 418 grains 38.9 mm 1894 Mo 416 grains 38.4-38.6 mm 1908 Mo 418 grains 39.3 mm 1891 As 416 grains 38.7 mm Can anybody else contribute to this database?
Even US Morgan dollars vary in weight. Absolutely. I've weighed hundreds and, although they weigh usually within a couple of hundredths of an ounce from each other, they vary! More wear usually doesn't mean much in weight loss. But Morgans were ALWAYS the same diameter and thickness. That's a good way to spot a fake Morgan if weight seems ok. Other factors too.
The difference in weighs for the coins mentioned here are too small to be significant on non-MS coins. The difference in diameter is due to differences in striking at the various mints. As you mentioned, sometimes the coins are not even perfectly round. And depending on the period, some have wider rims/dentiles than others. You would find similar difference in thickness as well. I am also fairly certain that the exact purity wasn't always 100% accurate, as you mentioned above as well.
