The ornamental design of the headset, as shown and described.
FIG. 1 is a front, left side perspective view of a headset of my new design;
FIG. 2 is a side elevational view of the headset of FIG. 1, with the other side being the mirror image of the view in FIG. 2;
FIG. 3 is a top plan view of the headset of FIG. 1;
FIG. 4. is a front elevational view of the headset of FIG. 1;
FIG. 5 is a bottom plan view of the headset of FIG. 1; and,
FIG. 6 is a rear elevational view of the headset of FIG. 1.
The broken lines shown in the drawings are for the purpose of illustrating the environment in which the headset embodying the design is used and forms no part of the claimed design or of a specified embodiment thereof.