i live in the area and am skeptical that ANYONE uses the full name in day to day contexts  the dominant newspaper salem news still uses manchester the police department answers their phone manchester PD high school students refer to manchester high  i understand the urge to distinguish itself from the muchlarger manchester NH nearby but IMHO this was really just a change on paper  the only time i hear anyone affix bythesea in day to day speech they also add technically  as in i live in manchesterwell manchesterbythesea technically  i think the article should be reworded to reflect that  that most locals use stuff doesnt pass my BS meter  but ill wait to hear what others think