Abstract: A generally rectangular flat housing is connected with one clamp of a self-centering work holder of an engraving machine for movement therewith. The housing slidably and pivotally supports a plurality of links connecting a control shaft with a pair of spaced-apart arms journalled by the housing for movement toward and away from each other in a pivoting action by the control shaft. When moved toward each other, the arms contact the respective opposing ends of a trophy plate to be engraved when loosely supported by the work holder for centering the trophy plate on the work holder prior to the engraving action thereon.