From my understanding it has been tested and it pretty close to 100% pure silver. I am not a big coin guy but we are trying to find out what it is or at least what country it is from.
It's something like this: http://www.ebay.com/itm/CHINA-Yunna...9658459?pt=US_World_Coins&hash=item564aa730db Your coin is actually one tael. Quite neat and expensive these days if genuine.
It is my father in-laws and he found it while fixing a water pipe in the 1980's in Austin,Tx. He said he had it tested and the guy said it is as close to 100% pure silver as it gets but he didn't know what it was. I saw it yesterday in a ziplock bag with some other coins and I told him I wanted to see if I could find out what it was, It has been in that bag for years I guess.
These were made from 1943 to 1945. They were used in indochina opium trade. If it's 35mm, or 1.37", it's a 1/2 tael. If it's 40-41mm, or 1.5" plus, it's a 1 tael. Two 1/2 taels sold for $157 and $184. A 1 tael is listed for $395. An AU 1 tael, cert by PCGS sold for over $1000. I'm sure their are fakes of them that exist. I would send it in to NGC or PCGS and have them certify it. Won't cost over 40 dollars, and would help the selling value increase tenfold.
First, welcome to the CoinTalk forum. Second, you would probably receive the best exposure & advice if you had posted this coin in the World & Ancients section of CoinTalk. Thirdly, I recommend that you wait for other opinions here or take it to a local coin show for opinions BEFORE you send it to a third party grading company like PCGS or NGC.
BTW, it is an interesting piece and I look forward to learning more about it as more people reply to your post.
Thanks for the post everyone, I had no idea where to start with this one. He has other coins that I might post up to see what y'all think.
Btw OP, I would also tell you to never have done what your father in law had done. You shouldn't need to test for silver content on a coin, since by that act you almost always damage the coins collector value in the test. A caliper, scale, and visual review is sufficient for 99% of authentication.