The Ferrocarril de Mejillones a Caracoles was a planned line that would have connected the Bolivian coast to the silver mines at Caracoles on the Altiplano, in today's Chile. Although the construction of the line only started in 1873, the first three Double Fairlies intended for that line were built in 1872 by Avonside. They had two groups of three driving axles each and carried the double works numbers 958-9, 960-1 and 962-2.

The locomotive shown in the picture was named “Escalador de Montes” or “Mountain Climber”. It is uncertain if all three actually arrived at the location of the new line. In 1877 the Bolivian government cancelled the contract since the Chilean-backed Antofagasta-Bolivia line ran in the same corridor. So ultimately, the Mejillones-Caracoles line was never opened and the fate of the locomotives is unknown.