Beginning in 1907, the Buenos Aires Great Southern received a series of Ten-Wheelers with different cylinder configurations from British manufacturers. The first was the class 12A with a two-cylinder compound engine, which was built a total of 32 times by Beyer, Peacock and North British and was later converted to simple expansion and superheated. Also in 1907, nine class 12B locomotives were built by the Vulcan Foundry, using four cylinder compound engines, three of which were superheated in 1924. In 1914 Beyer, Peacock built 20 class 12D locomotives, which had a simple two-cylinder engine and a superheater. 