The ornamental design for a double chaincollarkeeper, as shown and described.
FIG. 1 is a front elevational view of a double chain collar keeper showing
my new design;
FIG. 2 is a top plan view;
FIG. 3 is a side elevational view, the opposite side view being identical;
and,
FIG. 4 is a partial rear elevational view with part of the collar keeper
removed for ease of illustration, the portion not shown being a mirror
image of this view.