Hey Tony..... I am far from an expert on old Spanish Reale's. I did luck up after hurricane Hugo blew through my state in the 1980's and picked this one up off the coast. Genuine Spanish Reale's aren't all that rare, but man they are cool and represent an important historical period in our nations birth.... And for this very reason there have been untold numbers of copies made. You can go into many coastal gift shops in my state and find gift treasure boxes filled with pieces just like yours which does have the earmarks of being a cast replica. It is still a fun piece to have though.
The "style" (design) of your piece is rather crude. What does the edge look like? have you weighed it?
