AAA/Identity/Nac :: ACSv5.2 Actually Locate S/N Of ACS / VM Install To Open Case With TAC

I understand that on ACSv5 you can use either "show udi" or "show inventory" to find out the S/N of your ACS appliance....i.e. the S/N that you will use to open a TAC case....however, this particular install is a VM install and when I type either of those commands, under S/N the only thing I see is this: Serial: Cisco-VM-SN.how can I actually locate the S/N of ACS ona VM install to open a case with TAC?