What was found
AFTER MAJOR INSPECTIONS AT 145 REPAIR FACILITY, TO INCLUDE FIRE BOTTLE EXCHANGE DUE TO HYDROSTATIC TEST DUE, WE WERE ALERTED THAT THE EXCHANGE BOTTLE INSTALLED WAS THE INCORRECT PART NUMBER. THE PART NUMBER INSTALLED WAS FOR PRIOR SERIAL NUMBERS, AND WAS NOT APPLICABLE TO OUR AIRCRAFT. THE AIRCRAFT HAD FLOWN SEVERAL FLIGHTS BEFORE THIS WAS DISCOVERED. AIRCRAFT WAS GROUNDED AND BOTTLE WAS EXCHANGED FOR A CORRECT P/N.