One of the coins was chipped on the side and had a chisel mark, both probably from when a stack of coins were separated. When I showed them to Ed Krivoniak the expert coin cleaner in Pittsburgh, he said he had never seen any with this much corrosion. Ed, tried some diluted HCl on it and the hard surface didn't even react. The exposed copper metal near the chiped edge reacted as expected to the acid creating a porous surface. Not good.
I put it in Olive oil, then after one night, decided I didn't want to wait 6-months for the safe but slow reation. I then dumped it in very dilute HCl (probably 5% - 1 part in 6 diluted of muriatic acid which is 30%). It didn't seem to be reacting on it, so with my finger crossed left it overnight . After 12 hours the hard surface seems to have got soft but nothing had come off. I decided against keeping it longer and after washing it, dumped it into some jewelers E-Z Dip. That caused a bubbling reaction, so I scrubbed hard with a tooth brush. I had almost given up hope in seeing anything very clear.
And then like magic it was all there. On the obverse, a beautiful elephant with stretch trunk, three heap chitya, Tree in enclosure, flag and on the reverse the railed svastika, and upper part of the hour-glass figure. Wow, I have not had a thrill like this for a long time. I never expected that much detail under the very heavy crust.
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I suspect the surface under the corrosion which didn't separate easily
maybe bad. In such regions maybe the uncleaned corrosion will give
more character to this ancient coin.
Another extended session of cleaning did little to remove the remaining
corrosion. In any case no new detail became visible.
Few of the details on coin appeared to get weaker, and I have decided
to stop cleaning.
Clearly the cast-like nature of the coins from the same source and obtained by me in 2000 was from the trial by Fire the coin had been put through. The Elephant and Svastika coins from Ruhuna are probably struck like the coins found in Anuradhapura.
I will save the other E&S coin uncleaned till I learn the subtle tricks in cleaning ancient coins. I also hope I will be able to transfer some useful knowledge back to the source in Lanka to save some of the ancient coins from being damaged by fire.
The coin was scanned at 300 dpi and displayed at 200 dpi. It was obtained in 2003 May in uncleaned condition from Ratnayaka, a collector in Kataragama, Lanka.