Open back cap

FIG. 1 is a front perspective view of the open back cap showing my new design;

FIG. 2 is a rear perspective view of the open back cap thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a side elevation view thereof;

FIG. 5 is a top/rear perspective view of the design thereof; and,

FIG. 6 is a rear/side perspective view of the design thereof.

The partial human figure shown in broken lines in FIGS. 1-4 illustrates how the claimed design appears while being worn, and forms no part of the claimed design. The rear fastener shown in broken lines in FIGS. 5 and 6 is an unclaimed feature.