Irish schools grant the MB BS BCh (or some variant) degree. This is fully equivalent to the MD and recognized as such. If you do a residency in NAmerica after graduating from an Irish med school, you can keep your Irish degree or call yourself an MD (your preference). Basically, the MB degree (just like the Llb in law in the old days) are bachelor's degrees and the "newer" degrees (MD or JD for law) used in NAmerica are "doctor" degrees.