I found a fake 1885 Trade Dollar. 1885 Trade Dollar doesn't have any circulation strike. It just has Proof stike which is only 5. The 5 of this Trade Dollar is known. 5 of them are certfied coins. my "?": When there is a fake of a coin with only 5 genuine coins. One of this 5 owners had copied the coin?or it's a different story? the fake coin is low weighted.
The counterfeiter most likely made his obverse die from a genuine coin from another year and changed the date.
Like Hobo said, you might check the reverse to see if it is a type I or II design, if it is a type I (1873-1876) then that will give it away immediately. The obverse also has two types, so a type I (1873-1876) obverse would tell you something about the original date used. You may be able to narrow it down by the particular combination of type I and II obverse/reverses, which occur only in specific years.
