The Viceroy Toledo founded the Potosi Mint in December 1573, which began producing coins in 1574. The coins were marked by their designers with the initials "R" for Alonso Rincón and "B" by Juan de Ballesteros Narváez. The year 1616, during the reign of Philip III, marked a big change in the production of coins in Peru, as from now on the individual series were marked with the year of production.
The images of the above coin are the 8 Reales with the initial "B" for Juan de Ballesteros Narváez.