As you noted, the only way to verify grade for an absolute certainty would be to check the grade stamp beneath the left side lock plate. For all the owner knows the records are incorrect; or may have been misread due to the poor condition of the surviving records (and the fact that most entries were in pencil, now faded and often obscuring those hand written records even further). You will note that the new book revised Brophy's original A3 Grade count upwards from 17 to 18; this is due to the fact that one gun initially recorded as an A2 Grade because of a partially legible grade entry was correctly ID by the frame grade stamp as an A3. Typically, the Monogram grade mark on pre-13 guns is clearly visible on the water table, barrel flats, or both; if that is not the case, it would certainly behoove your friend to remove that lockplate screw and check the grade on the frame. Why, because an authenticated A3 Grade would be worth at least twice as much as a Monogram Grade in the same condition. If he doesn't think he can take the screw out without boogering the screw slot, he should visit a gunsmith. Now, tell us more about that 20-bore with an extra set of .410 barrels (what I really want is photos!).