A MD88 WAS DISPATCHED IN NON COMPLIANCE WITH #1 REVERSER DEFERRED AS INOP PER THE MEL; BUT NOT MECHANICALLY LOCKED OUT AS REQUIRED.

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WHEN WE REVIEWED ACFT'S LOGBOOK IN ZZZ; WE NOTED THAT THE L THRUST REVERSER WAS ON DEFERRED LIST. A REVIEW OF THE MAINT DEFERRAL MANUAL REVEALED THAT CIRCUIT BREAKER T-29 (REVERSER ACCUMULATOR LOW MESSAGE) SHOULD BE PULLED AND COLLARED. IT WAS NOT. WE CALLED MAINT AND HAD T-29 PROPERLY SECURED. THE FLT TO YYY WAS NORMAL. THE APCH WAS BRIEFED AND PLANNED FOR AN INOP L THRUST REVERSER. UPON LNDG; THE L THRUST REVERSER UNLOCKED AND DEPLOYED WHEN THE REVERSER LEVERS WERE RAISED. AFTER I CONFERRED WITH FLT CTL AND THE MAINT COORD ABOUT THE SIT; CONTRACT MAINT WAS CALLED. HIS INVESTIGATION REVEALED THAT THE THRUST REVERSER HAD NOT BEEN PROPERLY LOCKED OUT AT THE ENG. THE FLT BACK TO ZZZ FINALLY DEPARTED ABOUT 1 HR LATE; AFTER THE REVERSER HAD BEEN PROPERLY SECURED. I FOUND THIS ENTIRE SIT VERY TROUBLING. NOT ONLY HAD THE ORIGINAL MAINT BEEN PERFORMED IMPROPERLY; THE UNSECURED CIRCUIT BREAKER INDICATED THAT MAINT DEFERRAL MANUAL PROCS HAD NOT BEEN FOLLOWED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CREW FOUND THE CIRCUIT BREAKER NOT PULLED AND LOCKED OUT AND MAINT CORRECTED THIS DISCREPANCY; BUT NO THOUGHT WAS GIVEN TO THE MECHANICAL LOCKOUT OF THE REVERSER AT THE ENG. THE RPTR SAID ON LNDG THE REVERSER WAS ACTIVATED AND DEPLOYED.