 "D'Estrées" had served as the trial vessel for French variable depth sonar in the early 1960s.The armament was modified to two Mod 53 guns, one Mod 1972 375 mm sextuple anti-submarine rocket launcher, one Malafon anti-submarine missile launcher and two 20 mm guns.The Malafon system was installed aft with the magazine located directly in front of it.