Buckle

FIG. 1 is a front, left-side top, perspective view of a buckle, showing the new design; FIG. 2 is a front elevational view thereof; FIG. 3 is a rear elevational view thereof; FIG. 4 is a left-side elevational view thereof; FIG. 5 is a right-side elevational view thereof; and, FIG. 6 is a top plan view thereof, the bottom plan view (not provided) being a mirror image of the top plan view. The broken lines depict parts of the buckle that form no part of the claimed design.