The ornamental design for a barrel-shaped marker, as shown and described.
FIG. 1 is a front elevational view of the barrel-shaped marker of the present invention from a first side thereof, the other three sides (offset 90°C relative to each other) being identical.
FIG. 2 is a top, end view, of the barrel-shaped marker of the present invention.
FIG. 3 is bottom, end view of the barrel-shaped marker of the present invention; and,
FIG. 4 shows the barrel-shaped marker of FIG. 1 in an exploded condition.