I claim the ornamental design for a placket for a dress shirt, as shown and described.
FIG. 1 is a front elevational view of the placket for a dress shirt showing my new design; and,
FIG. 2 is an enlarged fragmentary front elevational view of the placket in the circular broken line of FIG. 1.
The circular broken line shown in FIG. 1 and 2 represent boundary lines.
The broken lines on the collar of the shirt represent stitching.
The broken line showing of a tie in FIG. 1 is included for the purpose of illustrating environmental structure and forms no part of the claimed design.