After the abdications of Bayonne in May 1808, in which Charles IV and his son Ferdinand VII renounced the Spanish throne, Napoleon Bonaparte granted the crown to his brother Joseph, who reigned from 1808 to 1814. It was a time of turmoil which, with the Peninsular War at its peak, and public opinion clearly opposed to the monarch, Joseph Bonaparte could only implement his reformist intentions in areas that were under the direct military control of the French army.
During the reign of Joseph Bonaparte coins were minted in silver with values of 10, 20 and 40 reales de vellón [billon real] (up to then, the real de vellón had been an accounting denomination, not a physical coin) and in gold of 80 and 320 reals, with an equivalence of 2.5 reales de vellón per 1 silver real, which means that the 20-real de vellón coin was equal to the old 8-real silver coin. Consequently, the 320 coin was equal to the 8-escudo coin.
The initials R.S. engraved on the reverse correspond to the assayers Antonio Rafael Narváez (R) and José Sánchez Delgado (S), who were in charge of marking the coins coming out from the Madrid Mint from 1810 to 1812.

Obverse: Nude bust of King Joseph I with infulae on the left. Striated . Everything surrounded by the legend and date:

IOSEPH NAP D G HISP ET IND R 1812

Reverse: Crowned shield with 6 quarters displaying the arms of Castile, Leon, Aragon, Navarre, Granada and the pillars of Hercules between two worlds representing the Indies with the Napoleonic imperial eagle in an inescutcheon. The value is expressed at the sides (320-Rs) and everything within the chain of the Order of the Gold Fleece. Encircling it all the legend the mark of the mint (M) and the assayers’ initials (RS). Striated . Surrounding everything:

AUSPICE DEO IN UTROQ FELIX M RS