If you did not enroll them into Casper once (and perhaps Unenroll then again so they would be Unmanaged but in the DB) before handing them out, or if this is a BYOD model.. the only thing I can think of is collecting info from your WiFi network or DHCP server. The first three pairs of the MAC address is tied to the manufacturer.
Our WiFi profile is only pushed out to those iPads that are Enrolled..
