The ornamental design for twin tray blank, as shown and described.
FIG. 1 is a top plan view of a twin tray blank showing my new design;
FIG. 2 is a front elevation thereof; the rear elevation being a mirror
image;
FIG. 3 is a bottom plan view thereof; and,
FIG. 4 is a right side elevation thereof; the left side elevation being a
mirror image.
The solid lines in the top and bottom plan views represent through cut
lines in the blank structure and the dashed lines in the top plan view
represent fold lines.