FLC OF MDT PICKED UP WRONG PREDEP CLRNC IN THEIR FLT PACKET WITHOUT NOTICING THE ERROR. ERROR WAS RECTIFIED BY DEP CTLR GIVING PROPER SQUAWK CODE.

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DEN USES PRE DEP CLRNCS (PDC'S). WE RECEIVE OUR PDC'S WITH OUR FLT PACKETS CONTAINING RELEASE; WX; NOTAMS; AND FLT DATA SHEET. DURING REVIEW OF THE PACKET; I DID NOT NOTICE THAT OUR PDC DID NOT MATCH OUR FLT. AFTER TKOF; DEP CTL GAVE US A CORRECTION TO OUR TRANSPONDER CODE. WE CORRECTED THE CODE AS REQUESTED AND THE PNF CHKED THE CODE ON THE PDC AND SHOWED IT TO ME AS THE ORIGINAL CODE. AGAIN; I DID NOT NOTICE THE WRONG FLT NUMBER; HAVING MY MAIN ATTN ON FLYING. AT THIS POINT; THE PNF NOTIFIED THE CTLR OF THE DISCREPANCY AS HAS BEEN REQUESTED. AT APPROX THE SAME TIME; THE PNF NOTICED THE ERROR IN THE PDC AND THE CTLR NOTIFIED US THAT THE CODE ORIGINALLY USED WAS FOR OUR FLT XXX -- THE PDC IN OUR POSSESSION; BUT NOT OUR FLT XXY. THE MIXUP WAS VERIFIED AND THE FLT CONTINUED WITHOUT INCIDENT. THE MIXUP WAS ALSO NOT NOTICED BY THE OTHER CREW. THEREFORE; THE ERROR WENT UNDETECTED BY THE ORIGINAL AGENT AND 4 CREW MEMBERS. AS SUCH ERRORS RARELY OCCUR; WE TEND TO BECOME COMPLACENT. I WILL CERTAINLY DOUBLECHK MY PAPERWORK IN THE FUTURE AS A RESULT OF THIS INCIDENT.