"iUnlocker" is a term historically associated with third-party unlocking services and verification tools. A check means:
Whether the device is (reported lost or stolen). The Sim-Lock status (Locked or Unlocked). If the device was a Replacement or refurbished unit. Summary of Check Methods What You Get *#06# Settings > General > About Full Details Serial, IMEI, Model Number Apple Support Website Warranty Info Official Coverage Status Verified Third-Party Tools Deep History Blacklist status, Carrier lock info Carrier lock info