There were nine shunting locomotives built for Cómhlucht Siúicre Eireann, Teoranta (CSET – translates as Irish Sugar Company, Ltd.) to work in their sugar beet factories.
They were allotted to three factories which were located at Mallow, Thurles and Tuam. Each site received three locomotives which they numbered independently of each other and hence there were three carry numbers 1, 2 and 3. The factories did however apply the numbers in different ways. The locomotives were swapped between factories on a regular basis and were moved between sites on the back of a Coras Iompair Eireamm (CIÉ) goods trains.
The locomotives were built in Germany by Orenstein & Koppel who were based in Berlin. The first six were produced in 1934 and the remaining three the following year. CSET chose O&K due to pressure from the Free State government to avoid conventional British manufacturers because of the ongoing Anglo-Irish trade war. The surplus of beef in Ireland bought about by this debacle meant that the first batch of locomotives were paid for by barter, with two shiploads of cattle sufficing as payment.
The locomotives were fitted with a funnel-shaped chimney (designed to accommodate a spark arrestor), outside valve gear, sanding dome, and unusual combination of side tanks and a well tank. They had a top speed of 30mph.
Two of the nine locomotives (No 1 Thurles and No 3 Mallow) have been preserved and are now based at the Downpatrick & County Down Railway (DCDR).