: Check for dead pixels, discoloration, or flickering. Test the touch response by dragging an icon across the entire screen.

: Obtain the IMEI number (found in Settings > General > About or on the SIM tray) and use an online IMEI checker to confirm it hasn't been reported lost or stolen. 3. Understanding iPhone Model Origins

: Inspect for deep scratches, dents, or signs of the device being dropped.

: Verify if the device is "Factory Unlocked." A locked phone will only work with the original seller's network.

The model number provides insights into the device's history (find this in ): If you want to buy a preowned iPhone - Apple Support