The last and heaviest Double Fairlies ordered by the Mexican Railway were the three members of the class R-3, numbered 183 to 185, which were built by Vulcan Foundry in 1911. They were ordered for the Orizabo-Esperanza line and had to haul 300 tons on inclines of 1 in 25, while negotiating curves of five chains (100 metres). To achieve the desired power, they weighed 138 tons with an axle load of 23 tons. This made them the heaviest and most powerful Double Fairlies ever built.

Despite their British builder, they had a typical American appearance. The water tanks above the boiler had a total capacity of 4,800 imperial gallons and made the complete locomotives look very bulky. This was further increased when they were converted to burn oil, with the oil tanks above the water tanks. Their careers ended in 1923 after the line had been electrified.