We claim the ornamental design for an article of jewelry having a secret message, as shown and described.
FIG. 1 is a perspective view of an article of jewelry having a secret message, showing a first embodiment of our new design in a collapsed configuration;
FIG. 2 is a perspective view thereof in a relaxed configuration;
FIG. 3A is the left side of a partial front elevational view thereof where the rear view, top plan view and bottom plan view are all mirror images;
FIG. 3B is the right side of a partial front elevational view thereof where the rear elevational view, top plan view and bottom plan view are all mirror images; and,
FIG. 4 is a left side elevational view thereof, the right side elevational view being a mirror image thereof.
The broken lines in the drawings represent environmental matter and form no part of the claimed design.