I claim the ornamental design for an extensible plate rim, as shown and described.
FIG. 1 is a front elevation view of an extensible plate rim;
FIG. 2 is a rear elevation view of the extensible plate rim of FIG. 1;
FIG. 3 is a right side elevation view of the extensible plate rim of FIG. 1;
FIG. 4 is a left side elevation view of the extensible plate rim of FIG. 1;
FIG. 5 is a top plan view of the extensible plate rim of FIG. 1; and,
FIG. 6 is a bottom plan view of the extensible plate rim of FIG. 1.
The claimed design for the extensible plate rim is directed to the portions shown in the figures and any portions not shown between the break lines form no part of the claimed design.