Shem,
The central horsebox was called up as 60M when it was brought into the CIE umbrella from MGWR. 12'4" high, 9' wheelbase, 15' chassis, build date 1901. There was a sliding panel Mike that slid up, and another that slid across within the doors. The two upper parts of the door hinged left and right, and the lower portion dropped down to the form the ramp. Beside that an infill panel, then a grooms door. The others in the rake appear to be DSER Ashbury horseboxes from 1879, but not 100% sure.
Meant to add that the annual fair in ballinasloe, up to 1500 horses would change hands, with up to 50 special trains operated to accommodate along with 25,000 sheep and 10,000 cattle. In CIE days at least 5 specials would operate.
Alphagrafix do a card kit of the MGWR horsebox, available from SSM, I believe.
Info from Des Coackhams Broad Gauge Carraiges, and H&D Railways in Ireland 1834-1984
Richie.