The 1350 foundation statutes for the College of Trinity Hall, Cambridge, contain unique provisions for a corporate signum or badge. The badge was specifically assigned to the college by its founder, William Bateman, Bishop of Norwich (1289–1355). Over time Bateman's personal arms replaced this signum in identifying the college and its property. The badge is often called Bateman's personal badge, but this is not supported by the statutes of the college or by the evidence of the badge's use in surviving books in the college library. The instructions for the college signum and its specific function in the marking of the college's books represents an interesting development in the indication of corporate, rather than personal, ownership using heraldic insignia. This paper discusses Bateman's instructions for the college signum and the evolution of the Trinity Hall arms.