FIG. 1 is a top, right perspective view of a heavy duty caliper showing our new design; FIG. 2 is a top plan view thereof; FIG. 3 is a left side view thereof; FIG. 4 is a bottom plan view thereof; FIG. 5 is a right side view thereof; FIG. 6 is a head on view thereof; and, FIG. 7 is a rear end view thereof.