DriveTrack units will have the serial number under the mount clip on the back. The serial numbers on Alpha 200i units will begin with '6EA' and Alpha 100 units will start with '2PV' or '3YU'. On Alpha handhelds, this will be located under the battery. Using this, we can check the item's purchase date and warranty status, or if out of warranty give a customer discount if the item was purchased from us. When you call Double U with a broken Garmin item, the first thing we'll ask for is its serial number.