Built in 1950 for the County Donegal Railways Joint Committee and purchased by the Railway Company at auction in September 1961 together with No.20, following initial trials the railcars were used extensively on winter services on the Peel Line, it being found they were not so efficient on the more heavily graded south line, particularly the climb out of Douglas Station.  The fleet numbers were retained by the railway though these were not actually carried externally for several years.  In fact, it was only with the purchase of No.18 Ailsa many years later that the gap in fleet numbering sequence was filled.  They saw regular use and were popular with enthusiasts, lasting in traffic throughout the Lord Ailsa regime.