The ornamental design for a seal, as shown and described.
FIG. 1 is a front view of a seal, the rear view being a mirror image of the front view;
FIG. 2 is a right side view of the seal of FIG. 1, the other side view being a mirror image of FIG. 2;
FIG. 3 is a top plan view of the seal of FIG. 1;
FIG. 4 is a bottom plan view of the seal of FIG. 1;
FIG. 5 is a cross-sectional view of the seal of FIG. 1 taken along line 5-5;
FIG. 6 is an enlarged detail perspective view of the outer circumferential surface of the seal of FIG. 1; and,
FIG. 7 is an enlarged detail perspective view of the inner circumferential surface of the seal of FIG. 1.
The dashed broken lines in the drawings are for the purpose of illustrating portions of the seal that form no part of the claim. The dash-dot-dash broken lines define surface boundaries of the claim, and indicate cutoff boundaries for enlarged detail portion views that form no part of the claim.