Peruvian sol coin. Image from Flickr by user Eddypedro, published with Creative Commons license (CC BY-SA 2.0).

The website Qué pasa [es] writes about the 150 anniversary of the Peruvian sol on February 14, 2013:

Central Reserve Bank of Peru (BCR) recalled that the change of currency was due to the invasion of feeble Bolivian currency that, since 1840, entered the country through the Southern zone, thus provoking confusion with the local currency.

Facing that situation, the currency reform replaced the Peso with the Sol, that would be coined with silver as well as with gold.