After Kitty, on the beach, puts on her skirt and dances over to pick up her top, you can see she's topless as she rises and turns her back to the camera. However, as she's towels off her hair, you can see a strap over her shoulder, and when she turns in surprise she's definitely got a top on.
Toward the end of the movie, Jimmy Cagney throws a hand grenade under the British armored car, but the subsequent explosion emanates from inside the vehicle on the upper side, while the undercarriage is completely unscathed.
O'Shea says he is a medical student at the College of Surgeons on St Stephen's Green (Royal College of Surgeons in Ireland), but the college scenes are all filmed at Trinity College, Dublin.