Disclaimer I have never worked with crypto machines and do not have access to any classified information. No classified information appears on this or any of my crypto db web pages. All the information is from open sources such as the internet and non classified manuals.
Army nomenclature, CSP-488 is the Navy name. The M-138-A is a strip cipher version. Used through the end of W. Used with a large number of radios for both voice, fax and data. Used with PRC-104 and other H.
What encryption system, what will it interoperate with? Replaces the KY-57 and other equipment. Uses a 40 character key based on 5-level paper tape. Originally designed to work with the PRC-77. Uses thumb-wheel switches to set key. There may be a shut down function that works by unit serial number.