No. 078 with a rake of Mk2Ds at Dublin Heuston in October 1985. ©Phil Richards
In 1972 CIÉ placed an order with British Rail Engineering Limited (BREL) for 72 new coaches based on the British Rail Mark 2d design. These were built at Derby Litchurch Lane Works. With air conditioning as a principal feature they became known as "AC Stock" and ran on type B4 bogies, with vacuum brakes. The order consisted of 6 First Class coaches, 9 Composites, 36 Standard Class, 11 Restaurant / Buffet / Standard Class and 11 Generator Vans. Internal fit-out was done in Inchicore, and was quite different from the original BR design, using bench seating rather than individual seats and made extensive use of wood veneer panelling. Their electrical system also differed from the BR and NIR versions. The Generator Van contained two engine / generator sets, each supplying 220 / 380 Volts 50 Hz AC to two separate "busses" in the train.
(Information provided by Wikipedia)