Milled coinage first appeared from New Spain in 1732, with the introduction of the screw press to the South American colonies.  Prior issues (known as cobs) were produced by method of hammered dies, resulting in crude, irregular shaped 'coins' which were quite unpopular in commercial trade. Production continued until 1771, when it was redesigned in favor of a bust style that carried the King's image.

The name 'pillar coinage' or 'columnario' is applied to this design due to the Pillars of Hercules on the (technical) reverse, which flank the crowned globes.  The scrolls which circle the pillars read 'Plus Ultra', which translates to 'Further Beyond', as reference to the original legend regarding the Pillars of Hercules which read 'Ni Plus Ultra', meaning 'Nothing Further Beyond'.  The two globes are a reference to the old and new world, both placed under the crown of Spain and circled with the coin's legend 'Utra Que Unum', or 'Both Shall Be One'.