The ornamental design for an escutcheon, as shown and described.
FIG. 1 is a left, top, front perspective view of an escutcheon embodying my new design;
FIG. 2 is a front elevational view thereof, the rear elevational view being identical to the front elevational view shown;
FIG. 3 is a left side elevational view thereof, the right side elevational view being identical to the left side shown; and,
FIG. 4 is a top plan view thereof.
The broken line representation of mounting structure in FIGS. 1 and 4 is for the purpose of illustration only, and forms no part of the claimed design.