I claim the ornamental design for an iron, as shown and described.
FIG. 1 is a perspective view of an iron, showing the new design.
FIG. 2 is an additional perspective view thereof.
FIG. 3 is a right side view thereof.
FIG. 4 is a left side view thereof.
FIG. 5 is a front view thereof.
FIG. 6 is a rear view thereof.
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
In the drawings, the evenly dashed broken lines depict portions of the iron that form no part of the claimed design. The dot-dash broken lines from a boundary to the claim and form no part thereof.