it could be one of 2 metros, A42 or A15, which collided head on outside of Mullingar in december 1963- seems to be the only reported accident at that time.
http://www.raiu.ie/download/pdf/accident_mullingar.pdf
according to the bible...
departmental vehicle no 1- GSR (ex MGRW)
inspection railcar no 6 - tralee/dingle lr
inspection cars no's 2-5 'drewrys' - GSR
looking up this stuff is a good excercise in learning railway history - some of these cars were really beautiful little things!