Built in 1951 for the County Donegal Railways Joint Committee and purchased by the Railway Company at auction in September 1961 together with No.19, 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.  At the time of nationalisation in 1978, in common with many other items of stock they were repainted from the familiar deep red and cream banding edged in black, receiving a black roof with cream upper panels and maroon lower sections, complete with fleet lettering but still without fleet numbers.  A further short-lived repaint came in 1982 when a blue and white scheme was applied but owing to the outbreak of the Falklands War legend has it that this was quickly redone owing to the resemblance to the Argentinian flag!  It was at this time that they were both painted red and white which was the standard bus livery at the time, and numbers were also applied to the cab ends.

By the 1990s they were largely relegated to departmental duties, years of neglect having seen the bodywork deteriorate to the point that they were not fit for the carriage of passengers.  They made some short trips as part of the Year Of Railways in 1993 but were withdrawn completely in 1998 and placed into storage.  In 1999 a rebuild was proposed and much work carried out but this was halted when it went over budget and the units placed back into storage where they remain today.  The Supporters' Association have been vocal campaigners for their restoration for several years and have had regular dialogue with the railway management to find a way forward for these historic items which have now spent the majority of their lives on the railway.  They are occasionally put on public display during summer events and still generate interest from visitors and enthusiasts alike.