The ornamental design for a caster, as shown and described.
FIG. 1 is a side elevational view of a caster showing my new design;
FIGS. 2 and 3 are respectively right and left end elevational views
thereof;
FIGS. 4 and 5 are respectively top and bottom plan views thereof;
FIG. 6 is a cross-sectional view of the side plate taken along the plane
indicated by line 6--6 in FIG. 4; and
FIG. 7 is a cross-sectional view of the side plate of a second embodiment
of the caster, it being understood that the second embodiment is identical
to the first except for the contours of the two side plates.