This is almost certainly a modern coin, not even really a reproduction. The "Piece of Eight" is a colloquial term for the Spanish 8 reales which was struck by the Mexico Mint in the mid-16th century until the mid-1800s.  The reales are round and feature the Pillars of Hercules surrounding crowned globes and ocean waves below, hence the other name for this coin, "Pillar Dollar".  The reverse shows a crowned shield with the assayers initials to the left and the denomination in reales to the right.   The above image is a real piece of eight.  As yours is a modern copy, it will be worth very little, if anything at all.