FIG. 1 is a perspective view of a coupling nut showing my new design, the broken line showing the threaded pipes being for illustrative purposes only and forming no part of the claimed design. The undisclosed portions of the threads and inner edges follow the contours of the sides shown;

FIG. 2 is a top plan view of the coupling nut shown on a reduced scale;

FIG. 3 is a bottom plan view thereof shown on a reduced scale;

FIG. 4 is a left side elevational view of the coupling nut shown on an enlarged scale, the right elevational view being identical thereto; and,

FIG. 5 is a front elevational view of the coupling nut shown on an enlarged scale, the rear view being identical thereto.