I claim the ornamental design for a coil storage unit, as shown and described.
FIG. 1 is a top view of the coil storage unit.
FIG. 2 is a front view of the coil storage unit. The back view is identical.
FIG. 3 is a right side view of the coil storage unit. The left side view is identical.
FIG. 4 is a bottom view of the coil storage unit.
FIG. 5 is a perspective view of the coil storage unit.
FIG. 6 is a second embodiment of FIG. 2, the only difference being the curvature of the cradle; and,
FIG. 7 is a second embodiment of FIG. 5, the only difference being the curvature of the cradle.
The design consists of the features of shape, ornament, pattern and configuration of the entire coil storage unit shown in the drawings. FIGS. 6 and 7 show a second embodiment of the coil storage unit in which the cradle is curved.