These coins were struck during the reign of Philip III (1598 to 1621) of Spain in the New World mint of Mexico.The obverse of the coins of this style features the Shield of the Hapsburgs with various sections and subdivisions in the shield for the various lands that the royals controlled. The shield was slightly different for each ruler and from each mint. The reverse features a Greek-style cross (with arms of equal length). Between the arms of the cross are Castles for Castille and Lions for Leon. Queen Isabella was queen of Castile and Leon when she married Ferdinand of Aragon. That union formed the nexus of modern Spain and their conquests of the remainder of Moorish Spain united the whole of the country under their aegis. Their only child, a daughter named Juana (or Joanna) married Philip the Handsome, a Hapsburg. That union brought many other countries and provinces to the Spanish domain. The Shield always features the Lions and Castles in the upper left quandrant (as you can see below in the photo of the back side of the earrings).
Spanish Colonial 1 real coins (1578-1621) and 24/22 kt gold. Obverse: Shield of the Hapsburgs with the Roman numeral I. Reverse: Greek-style cross with Castles & Lions.