If you will notice, most of the Trade Dollars out of China are represented by a picture of a good looking coin.  If you look closer, you will notice the date as 1872.  If you know anything about these coins, that should send flags flying immediately.  Trade dollars, as depicted, didn't start until 1873.  Also, why wouldn't they let you know the weight of the coin when you ask them?  The answer is that they don't have a clue.  If it doesn't weigh at least 28gm, you can consider it a fake or an altered coin.