EEE code found on part -- YKN, ZUH Note: All Apple parts have a special three digit "EEE" code embedded in the part serial number which positively identifies the part. Please note that this is the serial number of the part, NOT the serial number of the machine. The part serial number is on a tag which has the format "xxxxxxxEEEx". The "EEE" code is the three letters immediately preceding the last digit of the serial number.