There are several ways to tell if the coin is real or fake. First off weigh the coin. Second check the specific gravity of the metal. But, before you get nuts with it look over the coin. Look at the rim area.
The natural inclination is to look at the reeded (or smooth) edge of a coin to see if two coins surface areas where ground down and fused, glued, or whatever, together. In this case you look for a seam along the edges of coin. However, better fakes are made by boring out the center of one coin, and then grinding off one face of another coin that has had It's diameter reduced so that one coin can be inset into another. In this case a seem will show on the flat surface area of the rim itself. Beware. To make things worse, experts can add metal and fill in this area and emerory down this area to make it look real. This is when weight, specific gravity, and experiance, come into the equation. I hope your coin is real. Now that would be something. My guess? 6 figures. Hope this helps... Gusp