DePaul University in Chicago, IL requires padlocks, lock cylinders, and keys to be uniquely identified in order to track and organize them. Imagine not knowing which key fit which lock or cylinder set and multiply that by the number of students, faculty, and rooms on campus and you get a sense of the size of the problem. For over 20 years the DePaul University key shop used a holder and type set from Durable Mecco to mark each piece with a unique serial number.