As Don said, It's a Mexico mint cob, indicated by the Florenzada cross on the reverse. I'll add that the shield is of the Bourbon King, Phillip V, which dates a cob from 1700-1731, but seeing a bail soldered to the coin generally indicates a reproduction. What does it weigh? and why do you think it's a 4 real? The coins sulphided look can also be reproduced, and does not necessarily attribute to it's authenticity.