The COMPX Security Product DK4R Chicago Key Blank K-4-R is a tamper-evident security product that is designed to protect your business' most important assets. The DK4R is a unique key blank that is printed with your business' logo and contact information. The DK4R is a tamper-evident security product that is designed to protect your business' most important assets. The DK4R is a unique key blank that is printed with your business' logo and contact information. The DK4R is a tamper-evident security product that is designed to protect your business' most important assets. The DK4R is a unique key blank that is printed with your business' logo and contact information.