Oh, and other clues to look for, are missing or incomplete or wrong details. Notice that the dentils on this coin are extremely poorly formed, not to mention that weight is completely off. I believe the weight tolerance for trade dollars is either .16, or .11 grams. I cannot recall. Your was half a gram light, which even if real, would probably indicate some sort of major damage such as corrosion, rim filing etc. A lot of counterfeit coins get artificially circulated or get cleaned in order to hide evidence of counterfeiting such as raised lumps of metal or tooling marks. Your coin also has a granular appearance, and in this case, all of the deatails of the coin are very crude.