The Railways Joint Committee for County Donegal procured four tank locomotives to cope with the increasing weight of freight trains. With seven axles and a mass of nearly 45 tons, they were a substantial size for the three-foot gauge.
According to reports, the boiler originally had a poor steaming performance, which was attributed to an excessive number of heating tubes. Performance improved with the removal of the top row of tubes. In the 1920s, they were all fitted with a superheater, which again significantly increased performance.
The four locomotives were numbered 12 to 15 and named “Eske”, “Owenea”, “Erne” and “Mourne”. Three locomotives were scrapped in 1952 and 1954, but the “Erne” survived until 1968.