Your coin is a portrait dollar minted in Mexico City when it was a colony of Spain. Whether or not it is real is another question altogether since the coin is often counterfeited. You will also need to check the edge design very carefully, there should be an overlap in the "circle/rectangle" pattern exactly 180 degrees from each other and the design should be clear and consistent. Your coin with the HJ assayer is slightly scarcer than the more common JJ variety. Value depends on condition, a G/VG example starts about $45 and they climb from there with condition.