The offenders ordered the victim to lie on the ground, and they fled the scene.
Police have no suspects and have made no arrests in connection with the incident.
The 1957 Bronze Tablet is missing from the Main Library. The tablet, which usually hangs in a hallway of the library, was reported missing at about 3 p.m. Friday, according to a University police report. The Bronze Tablets honor students each year. No arrests have been made in connection with the incident. University police are investigating an attempted break-in of the bell tower in Altgeld Hall.