Using sportscard grading as an example, we employ field experiments to investigate empirically the informational role of professional certifiers. In the past 20 years, professional grading of sportscards has evolved in a way that provides a unique opportunity to measure the information provision of a monopolist certifier and that of subsequent entrants. Empirical results suggest three patterns: the grading certification provided by the first professional certifier offers new information to inexperienced traders but adds little information to experienced dealers.