The Defense Logistics Agency assigns a unique identifier (the “CAGE Code”) to provide for
“…a standardized method of identifying a given facility at a specific location. The code may be used for a Facility Clearance, a Pre-Award survey Engineering Rights, automated Bidders Lists, pay processes, source of supply, etc. In some cases, prime contractors require their sub-contractors to have a CAGE Code…”
As far as Systems Engineering is concerned, a CAGE Code is mostly used to uniquely identify a single Engineering Release Unit. At this writing, the list of CAGE Codes is accessible at http://www.dlis.dla.mil/cage_welcome.asp.