Mk3 coach at Dublin Heuston in 2006. ©Dawgz
Introduced on the CIÉ system in 1984 the last set was withdrawn on Monday 28 September 2009. The decision to purchase a new fleet of modern Intercity coaches based on the British Rail Mark 3 design was made because of several accidents involving the older style, wooden framed, coaches. They were already a well-proven design used for British Rail's High Speed Train (HST). The Irish Mark 3 coaches were similar, but not identical, to their British counterparts. They had a different electrical system (220/380V, 50 Hz) and were the first Mark 3's to be fitted with automatic swing-plug doors. There were also some different internal layouts more specifically suited to Irish traffic. Twenty-four coaches were built for push-pull operation on the suburban rail service including five built to Control Cars (6101–05, 6301–19). Originally used in conjunction with the 121 Class locomotives they were last used with 201 Class locomotives. There were a number of differences between the Irish push-pull Mark 3's and the standard Mark 3's. An underfloor generator, mounted in the Control Car, provided electrical power to the coaches; unlike on the standard Mark 3's, which used a special generator van.
(Information provided by Wikipedia)