What Is It 3?

Much like your #2, this coin features the lion of Leon on one side, and the castle of Castile on the other. That coin, of Philip II, has the legend HISPANIARVM REX, though. This one seems to have the same legend on both sides, ending in DEI GRACIA REX. This makes a true rebus on both obverse and reverse: ...by the grace of God, king of Castile / ...by the grace of God, king of Leon. The name "Spain" (Hispania) only really came into use after the heiress of Castile and Leon, Queen Isabella, married Ferdinand of Aragon. This design and legends belongs to the Trastamara kings of Castile and Leon, between 1369 and 1474. They were all Henries and Johns, but this coins lettering is too post-medieval for the earliest of the monarchs. I think each legend begins with ENRICVS, for Henry (Enrique) IV, on whose death Isabella became queen.