I buy a lot of stuff that I know nothing about.... Today I picked up a small pile of foreign coins. Nothing too exciting normally but I added a coin that is labeled at least as a ship wrecked cob. I’ve never owner a cob, held a cob or even seen a cob so I thought what the heck. It’s definitely in rough shape and, weirdly enough, smells like dirt. I took it to a reputable Local coin store and the XRF analyzer said it was right around 90% silver which I take as a good sign. It weighs 19.8g which I think is a bad sign as an 8 real should be heavier and a 4 real should be lighter. For what it worth the LCS thought it was real (no pun intended) but this is outside his expertise. I have no idea what I’m looking at. Any opinions and thoughts are appreciated. thanks.
I don't know if it's real or not, but that porosity makes it look like it's been underwater for quite some time. Looks like if could plausibly be a shipwreck coin to me. My only shipwreck salvage coin below. You can see the saltwater does a number on the surface. Silver will behave differently than copper Sweden, copper 4 Daler 1756. Probably underwater from 1783-1987 on the Nicobar wreck.
The weight is wierd. 8 reales come in at 27.4 grams, 4 reales half that at 13.73 and the fondness should be .93055
My fondness of this coin is under .93055. The weight is what has me most worried. Not sure if clipping & corrosion can account for the difference.
Saltwater corrosion can account for quite a bit of weight loss. Copper is much different from silver, but my 4 dalers weighs 1930 grams, and an intact one should be about 3060 g. So it's lost over 1/3 of its weight somehow. My impression is that cobs, in spite of their irregular shapes, were pretty close to a consistent weight. But all that pitting on the surface makes it quite plausible that a significant amount of metal has been lost. Below: Guatemala 8 reales 1739 cob
As my Scottish grandfather used to say, "I hae me doots" (I have my doubts) about this 8 reales. I have no personal experience of coins from shipwrecks and their loss of weight, so its current reduced weight could perhaps be explained away. On the other hand, I am pretty certain that it can't be from Mexico. The letter O (if it is an O) on the left of the shield is much too low down. There isn't room for the M below the O and then the assayer's mark below the M So could the O be the assayer 's mark below the Mexico mintmarkO M which are What is more, there wasn't an assayer in Mexico whose mark was an O or a C or G on the
I hit the Post button before I had finished writing. I was trying to say that the O or C can't be the assayer's mark because there was no assayer in the Mexico mint who used the initial O or C
