The Caledonian Railway's class 812 comprised 79 0-6-0 freight locomotives, which McIntosh had developed as a successor to his “Jumbos”. They differed primarily in their larger boiler and longer wheelbase. The boiler was the same as that of the Class 721 “Dunalastair”. After the class 812 had been built by three commercial manufacturers in 1899 and 1900, the CR built 15 identical locomotives as class 652 in 1908 and 1909 in its own St. Rollox workshops in Glasgow.

They could reach a speed of up to 55 mph or 89 km/h and were therefore also used in passenger service. For this 17 had got a continuous Westinghouse brake. A necessary improvement concerned the frames, which had to be reinforced due to cracks.

After the founding of the LMS, these locomotives were put into the power class 3F and distributed across most of Scotland. When British Railways were founded in 1948, almost all of them were still in use. It took until 1963 for all to disappear. Only number 828 remained and is now operational and owned by the Strathspey Railway. The Belgian State Railways purchased a total of 891 locomotives in three types that were directly derived from these.