These locomotives were manufactured in 1957 and its main difference when compared to the existing G12s is the truck equipped with 3 axles. The centered wheel, with smaller diameter, non powered, would be used only for distribute the locomotive´s weight. That´s why they are classified as G12 A-1-A.
The Viação Ferrea Rio Grande do Sul (FVRGS) bought 20 of these locos in 1957, in a time where the company was not incoporateed by RFFSA (Rede Ferroviária Federal S.A). When that happened later on, the painting had to be changed and the A-1-A boggies were replaced by "B" trucks to be used in other RFFSA sections.
Even tough, in Brazil its representation is not so huge, in other countries like Taiwan, Australia, New Zealand, Argentina and East Asia they were pretty useful and even remarkable.