I would like to see at least a specific gravity test (but that could also be faked), or better, pay a deposit on a drilled sample (but even then there could be a switched sample), I do not think without being there and testing it for youself you would be able to tell untill after you lost your money or did not.
I would bet the chinese could make them bars to almost fool specific gravity and density by size ratio's, and stamp with certified numbers, that is alot of money to order a hunk of metal on some ones word a picture or hoping if it was not real you may get your money back.