cooperating {HEAD ~ means} on {TAIL ~ each} of said display cases for retaining adjacent display cases releasably in vertically stacked relation for pivotal movement of their front and rear compartments as units about a common vertical axis, and 
on
cooperating { HEAD ~ means } on { TAIL ~ each } of said display cases for retaining adjacent display cases releasably in vertically stacked relation for pivotal movement of their front and rear compartments as units about a common vertical axis , and
OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH