THE CREW HAD COMPLETED A CORE TUBE RETREIVAL AND WAS PREPARING TO REMOVE THE STUFFING BOX AND OVERSHOT. THE DRILLER'S ASSISTANT BEGAN UNTHREADING THE STUFFING BOX WITH A PIPEWRENCH AT WHICH TIME THE STUFFING BOX, OVERSHOT AND TUBE FELL ON TO THE ASSISTANT'S RIGHT FOOT FROM A HEIGHT APPROXIMATED AT 4 FEET.