Not able to locate device on my network of MAC address produced by "show mac address-table" or "show bridge-address-table"

Hi,

I am still trying to track down some odd STP RSTP issues and came across a strange listing when I tried to list the MAC addresses seen by my switches.

There are several unique Dell Switch(?) MAC addresses that I can't find anywhere on our network.

I can view the MAC addresses on all my active switches through the GUI using "show asset" but there are about six MAC addresses in my list that aren't listed anywhere and they are definitely Dell switches (00:13:72:x:x:x, d0:67:e5:x:x:x, 00:25:64:x:x:x) 

Is there some way to list all the native MAC addresses associated with a particular switch?