Abstract: A method and apparatus for identifying cast parts. A master is provided at least partially formed in the shape of a part to be cast. A slot is then milled into the master, the slot having a mouth and a base, and the slot having a "dovetail" cross-section so that the slot is wider at the base than at the mouth. An expandable plastic tag is inserted into the slot. The tag includes an identification surface with indicia formed thereon. Finally, the master and tag are heated, causing expansion of the tag within the slot to secure the tag within the slot. The tag includes a pair of tabs extending laterally therefrom to secure the tag in the slot prior to heat expansion of the tag.