This BEST interchangeable core (IC) is shown with a dedicated control key attached by a ball chain, demonstrating a practical setup used by maintenance and security teams for rapid access and rekeying. The IC system, pioneered by BEST, allowed facility managers to replace cores on-site within seconds, using this control key to release and install cores without dismantling the lock. Frank Best filed the original IC patent in 1921 and continued to improve both product and manufacturing processes throughout his career, ultimately securing more than 100 patents. The visible wear on the brass housing and classic BEST key stamping marks decades of widespread use in institutional and commercial settings.
