The model number is due to its storage capacity — 64 kibibits (65,536 bits, or 8 KiB), enough to store multiple encryption keys.
In case of loss, the user gets a new CIK, effectively changing the lock in the cipher machine, and gets back in business.
The CIK device is simply an empty register which can be supplied with its unique sequence from the randomizer function of the parent machine itself.
The effect of this procedure is to provide high protection against the covert compromise of the CIK wherein a thief acquires the device, copies it, and replaces it unknown to its owner.
This concept appears particularly attractive in office environments where physical structures and guarding arrangements will not be sufficiently rigorous to assure that crypto-equipments cannot be accessed by unauthorized people.