What was found
DURING INITIAL CLIMB, AS FLAPS WERE RETRACTING 5 TO 1, AN AMBER REVERSER MESSAGE APPEARED FOR THE LEFT ENGINE. DECLARED AN EMERGENCY, PERFORMED QRH PROCEDURE, RETURNED TO DEPARTURE. RUMBLE & VIBRATION NOTED ABOVE 120 KIAS. PERFORMED UNUSUAL CONDITION INSPECTION IAW AMM 72-00-00-206-096--H00, AND ENGINE POST WINDMILLING INSPECTION, OPS CHECKED NORMAL.