An heirloom was a possession or valuable object that has belonged to a family for more than one generation. It is sometimes a form of inheritance.
In 2152, T'Pol's family owned a Human purse as an heirloom that was given to them by her ancestor, T'Mir, who aquired it after crash landing on Earth in 1957. (ENT: "Carbon Creek")
In 2373, Michael Eddington owned an heirloom in the form of a Canadian one dollar coin he called his "lucky loonie", which had been in his family for over two hundred years. (DS9: "Blaze of Glory")
Vau N'Akat heirloom[]
In 2383, Gwyndala possessed a Vau N'Akat item she referred to as "her heirloom." It was a brass-colored bracelet worn around her upper arm. The heirloom was made from a malleable metallic matter with unique properties that allowed her species to manipulate it into various forms like a blade, a shield, or a leg brace using a kind of psychokinesis.
With concentration, Gwyndala could also move the heirloom independently of her body, although if it was damaged it took considerable mental strain to reform it. Gwyn claimed it was the only thing her father, The Diviner, ever gave her. (PRO: "Lost and Found", "Dream Catcher", "Terror Firma")