Author Topic: Japanese bita-sen found in central Vietnam  (Read 74 times)

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Offline bgriff99

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Japanese bita-sen found in central Vietnam
« on: February 10, 2019, 08:21:50 AM »
Some bita-sen, exported from Japan circa 1600-50.    Metal content tends to have considerable amounts of iron and arsenic.    Strangely, they can combine, if the arsenic exceeds the iron level, into a non-magnetic compound.    Such a coin can have above 12% iron and be nonmagnetic, while one with 1% iron and no arsenic will be magnetic.

Offline THCoins

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Re: Japanese bita-sen found in central Vietnam
« Reply #1 on: February 10, 2019, 11:52:24 AM »
Beautiful patinas on these specimen, and such a range of colors !
I guess that's both the result of metal composition and the surrounding in which it was preserved.
Interesting observation about the magnetism. Since i standard have a small strong magnet on my desk i have been surprized by how many coins which i thought of as billon or bronze turn out to be magnetic. But that's in north-Indian medieval coinage. Here the presence of magnetic coins seems to correlate mostly with times of political crisis.