Bishop Slattery preferred to display emblems which are significant to him personally. The principal figure is the arms of the Catholic Extension Society - where Bishop Slattery was associated since 1971 and President from 1976 - to which are added a gold crescent. The Extension arms are a silver field bearing a red cross with blue sidebars. The red, white, and blue symbolize the long history of Extension's involvement with American home missions.

Extension arms have particular significance for Oklahoma Catholics. Not only has the church benefited from Extension generosity, but three of Extension's former officers have become bishops in Oklahoma: Bishop Francis Kelley, Bishop Eugene McGuinness, and Bishop Slattery.

The gold crescent moon which personalizes the arms for Bishop Slattery represents Mary, the Mother of God, whom the Church traditionally refers to as "a woman clothed with the sun, with the moon at her feet." Mary also is significant of Bishop Slattery's home parish in Chicago, the Visitation of the Blessed Virgin Mary.

The upper part of the shield bears a golden sun bearing the Monogram of Jesus (the IHS with a cross through it) in red. This is a Jesuit symbol, special to Bishop Slattery who was educated by the Jesuits at Mundelein. The sun appears against a field of green, a color associated with Ireland. By including green, Bishop Slattery pays tribute to his Irish heritage. Both sets of the bishop's grandparents emigrated to the U.S. from Ireland.