Years ago I was told by a collector whom I believe correct that what I called reticulation on that old page:
was a pretty certain sign that a coin is genuine (at least ancient). There is an important distinction between this condition and what I'd call porosity which is caused by corrosion and can be induced by chemicals. On my page I commented, " Note that the surface is reticulated with continuous high ridges separated by short (dark) recesses rather than scratched which would show continuous (dark) recesses. " I stand by this definition. Crystallization of the type I showed should take a few hundred years to develop (I do not claim to have a handle on this time line) and would be hard to simulate through artificial means. It only seems to occur on coins of a relatively high grade silver. Billon coins which break with similar ease show a completely different 'grain' pattern. There does seem to be a middle ground of alloy which does not develop either fault. This includes coins of both the US and Sterling standards so I do not expect to find what I called reticulation on a US or British coin from the 1700's. I would be interested in seeing photos showing that I am wrong here. The holed coin shown above is a great example and well photographed. I wonder how much a drop it would take to break a reticulated coin but I am not sufficiently interested to put that question to the test.
I might add that there are some relatively high silver coins that show no surface pattern but have broken from a little drop. I am not sure what is happening in those cases and hope someone can explain it. Was not there a dekadrachm of Akragas broken at a sale from a drop? I do not recall if it showed signs before or not.