Unum e pluribus 1787 nova?
You should first examine the coin to see if it has the word "COPY" on it. There have been many replicas of Continental coins struck over the years. Some were for novelty collectors' sets and others are outright counterfeits (which, of course, would NOT have the word "COPY"!)
Given that, it's not likely the coin is genuine. If you want to make absolutely certain, it would have to be examined in person by someone who deals in early U.S. coins.