KYK-13

The KYK-13 Electronic Transfer Device is a common fill device designed by the United States National Security Agency for the transfer and loading of cryptographic keys with their corresponding check word. The KYK-13 is battery powered and uses the for key transfer. Its is 5810-01-026-9618.p

Even though the KYK-13 is several decades old and was supposed to have been obsoleted by the AN/CYZ-10 Data Transfer Device, it is still widely used because of its simplicity and reliability. A simpler device than the CYZ-10, the KIK-30 "Really Simple Key loader" (RASKL) is now planned to replace the KYK-13s, with up to $200 million budgeted to procure them in quantity.

...
Wikipedia