From the IBM Archives site (http://www-03.ibm.com/ibm/history/exhibits/system7/system7_intro.html, checked 3/19/2014) this is "The processor module and from one to 11 input/output modules were housed in enclosures (IBM 5026) that also provided internal power supplies, signal distribution, and an operator console." A key and a small screw found with the object are bagged and attached.
International Business Machines Corporation (IBM)
Found on back panel label
#14 IBM S/7
Computer Museum Aachen deprecated registration number on adhered label on left side panel