Coupling

FIG. 1 is an isometric view of a top, front, and right side of an ornamental design for a coupling;

FIG. 2 is a front elevational view of the coupling of FIG. 1 ;

FIG. 3 is a rear elevational view of the coupling of FIG. 1 ;

FIG. 4 is a right side elevational view of the coupling of FIG. 1 ;

FIG. 5 is a left side elevational view of the coupling of FIG. 1 ;

FIG. 6 is a top plan view of the coupling of FIG. 1 ; and,

FIG. 7 is a bottom plan view of the coupling of FIG. 1 .

The dash-dash-dash lines illustrate portions of the coupling that form no part of the claimed design.