Marcia is an old, but well maintained pre-war service weapon, used by Thomas Hamilton. It is a reliable and somewhat powerful weapon that has served Hamilton well. It was named after its previous owner, who was a missionary, who hunted Hamilton down.
Marcia's moral convictions got the better of her, causing her to cave and loosen her grip on her gun. Hamilton took it and shot her with it.
Marcia was destroyed, along with Denis' Revolver during the battle of Megaton.