The ornamental design for a mug or similar article, substantially as shown and described.
FIG. 1 is a top perspective view of a mug or similar article showing my new design;
FIG. 2 is a rear elevational view thereof, the front elevational view being a mirror image thereof;
FIG. 3 is a right side elevational view thereof;
FIG. 4 is left side elevational view thereof;
FIG. 5 is a top plan view thereof; and
FIG. 6 is a bottom plan view thereof.
The broken line showing of a handle in FIGS. 1, 2, 4, 5 and 6 is for illustrative purposes only and forms no part of the claimed design.