I think as they were building the coaches they were morphing from Mk2b into Mk 2c 4112 also has two roof hatches? , The vents are what were called 'GM vents' I belive very similar to what were on the cravens , most Mk2c had Roe Vac vents . Whatever chances we have of seeing some MK2b's and Mk2c's in IE/IR livery I doubt 4112 would be one of them as it a total oddball .