The FBI asked for the SW. They did not demand it but said Apple “may” supply it as long as they tie the SW to the phone. They gave two examples of how to tie it to the phone. First the serial number which is on the back of the phone. But the serial number is not accessible in SW as of iOS 8. Apple provides an alternative ID on the screen. The IMEI is on the SIM and the SIM is removable so it obviously cannot be used to ID a phone.
They identified the specific device the order pertains to.